随着自由贸易协定（Free Trade Agreement, FTA）数量的逐渐增加，世界贸易体系呈现出一国与多国之间的FTA重叠复杂关系网络，这种复杂网络关系会进一步影响一国签订FTA的意愿，即产生感染效应。为了考察该效应，本项目首先针对四种不同FTA网络关系情形下的感染效应进行理论分析，对不同情形下一国签订FTA的意愿进行比较与排序，以证明感染效应的存在；其次，本项目在Baldwin & Jaimovich（2010）的基础上拓展感染指数，为度量不同FTA关系网的感染效应提供更有效的方法，并分析感染效应的影响因素。最后，运用所拓展的感染指数，从中国角度出发，对感染效应进行实证度量。本项目的研究，能够为一国谨慎、理智地选择FTA贸易伙伴提供决策依据；同时本项目拟拓展的感染指数，能够为FTA的可行性研究提供更有效的实证方法；最后，本项目的实证研究结果，对中国未来FTA发展格局具有指导意义。

With the increasing number of FTAs, a country may has built one or more FTA relationships with others, and world trading system presents a complex and overlapping FTAs network. Such a network of relationships further affects the willingness of a country's FTA, that is, produces the contagion effect. To investigate this effect, firstly our project make theoretical analysis of the contagion effect in the case of four different FTA networks, comparing and sorting the effects in different circumstances. Then we analyze the determinants of the contagion effect, and added spatial geographic factors to expand Baldwin & Jaimovich (2010) contagious index, with the goal of providing a more effective method for empirical measure. Finally the expanded contagious index will be use to conduct empirical measure the contagion effect of China. This study will furnish the base for decision-making for a country to selects FTA trading partners with rational reasons; and the expanded contagious index is able to provide more effective method for the empirical measure. What's more, the empirical results of this project have a guiding significance of China's future FTA development patterns.