由于山地区域特殊的地理条件，大规模的城市建设往往受到诸多局限，因此，小城镇建设对于山地区域的发展便承担起了重要的作用。我国西南地区是典型的山地集中区、山地面积占比高达90％，这一地区小城镇数量众多，自然和人文景观资源丰富，从而提高了对西南地区小城镇可持续建设的要求。基础设施对小城镇的建设发展起着至关重要的作用，基础设施可持续建设的水平极大地影响了小城镇可持续建设水平。然而，由于西南地区经济基础相对较差，基础设施投入资金总量有限、各类基础设施投资分配不合理，使得山地小城镇普遍存在基础设施可持续建设不足的问题，从而制约了山地小城镇的可持续发展。十九大报告中强调，我国社会主要矛盾已经转化为人民日益增长的美好生活需要和不平衡不充分的发展之间的矛盾，发展不平衡包括城乡发展不平衡、地区不平衡、人群不平衡。因此，关于山地小城镇基础设施投资组合问题的研究，对解决我国西南地区小城镇基础设施可持续建设不足的问题、改善基础设施建设条件、落实我国新型城镇化战略以及解决我国当代主要社会矛盾中发展不平衡问题均具有一定的现实意义。 鉴于此，本研究以基础设施投资带动山地小城镇可持续建设为立足点，以“现状分析——作用研究——优化模型构建——实证分析”为研究思路，将基础设施投资对可持续建设的贡献作用大小作为衡量标准，探索山地小城镇基础设施的最优投资组合，为提升山地小城镇基础设施可持续建设水平寻找解决方案。论文具体按照如下逻辑顺序展开研究： 首先，论文从山地小城镇、基础设施可持续建设等相关概念的界定出发，通过对可持续发展理论、公共物品及外部性理论、资源最优配置理论和投资组合优化理论的认识，以及围绕山地小城镇建设与发展、基础设施可持续建设及评价和基础设施投资这三个方面对国内外已有研究的综述，全面而又有所重点地把相关理论和相关文献研究进行了归纳和提炼，为全文的研究奠定了理论支撑。 第二部分，通过文献研究法和专家访谈法筛选出西南地区山地小城镇最主要的五类基础设施：道路交通、污水处理、垃圾处理、供水和燃气设施，并就其建设内容和投资现状分别进行了剖析，从而界定了研究的对象和范围。 第三部分，论文围绕“作用论证-作用方式与路径分析-作用强度评价”的逻辑思路，系统而深入地展开了山地小城镇基础设施投资对可持续建设的作用的研究。论文首先利用问卷调查、专家访谈、结构方程模型等方法，通过对山地小城镇基础设施可持续建设的障碍因素识别，发现了投资方面的因素是最大障碍因素，论证了投资对山地小城镇基础设施可持续建设的突出作用，并将投资组合优化作为有效解决途径。接下来，论文分别从整体和个体剖析了基础设施投资对可持续建设的作用方式和影响路径。最后，为了找到“作用强度评价”的方法，论文提出了“可持续贡献度”的概念，并利用文献研究法、专家访谈法、熵权法等方法构建了由23项具体指标组成的综合指标体系和可持续贡献度评价模型。 第四部分，投资组合优化方法的研究是本文的重要内容。为了给投资组合优化奠定基础，本文基于投资组合理论探讨了“投资-可持续贡献度”关系下基础设施投资组合优化的基本原理，提出了基础设施“动态投资效应”的概念、用以具体剖析各类基础设施投资处于不同阶段所实现的可持续贡献效果，并结合蒙特卡洛模拟法、概率分析法构建了基于可持续贡献度评价的基础设施投资组合优化模型。 最后，论文以重庆市建胜镇为例，将本研究构建的基础设施投资组合优化模型在建胜镇进行了应用，找到了适用于该镇、以可持续贡献度最大化为目标的投资组合方案。通过实证分析，对理论模型进行了应用，并验证了模型的实际意义和实践参考价值，为山地小城镇基础设施投资决策提供了重要的参考依据。 本论文通过理论模型构建和实证分析，探索了基础设施投资对可持续建设的作用，提出了“可持续贡献度”、“动态投资效应”等概念，构建了基于可持续贡献度评价的指标体系和不同类型基础设施投资组合优化模型。本研究成果对丰富相关领域的研究具有一定的理论贡献，也对我国西南地区乃至全国山地小城镇基础设施投资决策与管理具有一定的参考价值。 关键词：山地小城镇，基础设施，投资组合，可持续建设，西南地区

 Mountainous regions are not suitable for larger scale construction due to the special geography and location. Therefore, townships play an important role in the development of these regions. Southwest China is a mountainous cluster because most of the region is covered by mountains which account for over 90% of the land area. There are a large number of mountainous townships in Southwest China, with outstanding cultural characteristics and ecological landscape, which indicates restrictive environmental protection and higher requirements for sustainable construction. In view of the important role of infrastructure on townships development, infrastructure sustainability is the key for sustainable construction of townships. However, the investment to infrastructure is very limited because of the relatively weak economic base in townships in Southwest China. As a result, infrastructure sustainability in China's mountainous townships is poor. On the whole, the insufficient investment supply restricts the infrastructure sustainability and the sustainable development of townships. According to the reports of the 19th National Congress of the Communist Party of China, the major social contradiction in our country has been transformed into the contradiction between the people's growing needs for good life and the unbalanced development. The unbalanced development includes urban and rural development imbalance, regional development imbalance, and population development imbalance. Therefore, research on infrastructure investment portfolio in mountainous townships has great practical significance not only to improve poor infrastructure sustainability in mountainous townships in Southwest China but also to implement China's new urbanization strategy and solve the unbalanced development of the major social contradictions in our country. In view of the background and research purpose, based on the foothold of infrastructure investment to drive the sustainable development of townships and the research route of "analysis of current situation -- analysis of function relationship -optimization model construction -- empirical analysis", with the measurement of the contribution of infrastructure investment to sustainable construction, this research aims to explore the optimal infrastructure portfolio in mountainous townships in order to improve the poor infrastructure sustainability. The major research works are as follows: Firstly, beginning with the definition of related concept such as mountainous townships and infrastructure sustainability, application of the theory in this paper have been discussed including the theory of sustainable development, the theory of public goods and externalities, the theory of resource optimal allocation and the theory of portfolio optimization. Furthermore, with literature review including the construction and development of mountainous townships, infrastructure sustainability and assessment, and infrastructure investment, the related theories and related researches have been concluded and extracted so as to lay theoretical foundation for the whole research. Secondly, in order to concentrate on key points and in-depth study, the main five types of infrastructure, including road, sewage treatment, waste treatment, water facilities and fuel gas facilities, in mountainous townships in Southwest China have been identified by applying document research and experts interviews method. Accordingly, the construction content, investment characteristics including investment composition and exiting problems are all analyzed. Thirdly, this study employs the questionnaire survey, experts interviews, exploratory factor analysis and structural equation modeling to identify the constraints to infrastructure sustainability in mountainous townships. The analysis results demonstrate the important role of investment in infrastructure sustainability and indicate portfolio optimization as an effective solution. Moreover, in order to find the quantitative method of the function relationship between investment and infrastructure sustainability, this paper analyzes the influence mode and influence path of infrastructure investment on sustainable construction from the whole and the individual infrastructure respectively. Then, based on the proposed concept of “sustainable contribution”, a comprehensive index system with 23 specific indicators and an evaluation model of “sustainable contribution” have been constructed. Fourthly, in order to lay a theoretical foundation for portfolio evaluation, this paper puts forward the concept of “dynamic investment effect” of infrastructure which explains the effect of sustainable contribution according to different infrastructure investment scale. Combined with Monte Carlo simulation method and probabilistic analysis, a portfolio optimization model based on comprehensive sustainable contribution evaluation is constructed. Finally, the practical significance and reference value of the model are verified through empirical analysis about Jiansheng Town in Chongqing. The study provides important references for the infrastructure investment decision in mountainous townships. Through theoretical model and empirical analysis, in this study, the function of infrastructure investment on sustainable construction has been explored, concept of “sustainable contribution” and “dynamic investment effect” has been proposed, an assessment index system of sustainable contribution and a model of different types of infrastructure investment portfolio optimization have been constructed. The result of this study could contribute to enrich related research and provide useful guidance on infrastructure investment decision-making and management for mountainous townships in Southwest China and even the whole country. Keywords: Mountainous Townships, Infrastructure, Investment Portfolio, Sustainable Construction, Southwest China