Abstract: The study of the social capital and its relationships with the development is a topical subject. As one of the important factors affecting the sustainable development，social capital plays a very important role in the social and economic development in a country or region. This paper takes Zhangye City，Gansu Province，China as the research area，in which it is famous for “The Silk Road”，and designs the measurement index of social capital．It uses the farmer households survey datas and principal component analysis method to calculate social capital index and then analyzes the social capital factors．Finally，the paper also analyzes the factors that are influencing the social capital. The results show as follows：（1）Social capital index in Zhangye City is 4.93. The trust and solidarity dimension maintain the highest development level，while the information dissemination dimension maintains the minimum development level. （2）There are hosts of differences in the influencing factors of different dimensions of the social capital．The factors influencing the trust dimension basically are the householders' educational level and the wealth differences. The factors influencing the political empowerment dimensions are the householders' educational level and the age of the head of the household. The factors influencing the network dimension are the householders' educational level、the average annual income and the age of the head of the household. The influencing factors of the cooperation dimensions are the householders' educational level、the average annual income and the age of the head of the household and the wealth differences. The influencing factors of the social cohesion dimension are the householders' educational level、the age of the head of the household and the wealth differences. However，the influencing factors of the information dissemination dimension are the householders' educational level、the average annual income and the wealth differences among the householders. （3） The stock of social capital can be improved increasingly. It is significant to strengthen the investment and construction of the trust dimension、develop the folk organizations to improve the ability of obtaining the information by the telephone、the internet、the TV and so on and continue to make the officials and the villagers committee serve the people heart and soul. Meanwhile，local government should increase the opportunity of employment with local conditions、strengthen infrastructure construction to improve the telephone and the internet coverage and held "science and technology culture month" activities to improve their education level.

Key words: social capital, infwencing factors, households, Zhangye City