China's rural areas introduced the Microcredit model of Bangladesh Grameen Bank (Grameen Bank) in 1993, and Chinese Government ever since attached importance to it. In fact this model places the farmers into a specific repayment mechanisms. This paper will use the knowledge of game theory to figure out the key factors that impact the farmers’ repayment. Meanwhile, based in the actual conditions of micro-credit business in China, and seizing the opportunity that Postal Savings Bank of China was allowed to business, the paper will try to analysis how to increase the farmers’ repayment rate according to the results of theory and solve some problems in the current operation of the system. At last, the paper gives some relevant recommendations to Postal Savings Bank of China for the development of rural micro-credit system.