Abstract: According to the commercial integrity that plays an important role in the cooperation between bank and enterprise, the credit relation between them is studied on the basis of the principal-agent theory and centipede game theory, etc., and the credit process is divided into two stages, i.e., one-time game and repeated game. In the one-time game the phenomenon of reluctance to loan is explained, and in the repeated game the optimal cycle of cooperation is determined, as well as the minimum expected credit rationing of the enterprise applying for loan. Such a mechanism will avoid the adverse selection and reduce the moral risk in the credit process to a certain degree.