By using the allocation of guarantee rate saving as incentive mechanism and introducing the influence coefficient of the SMEs in mutual guarantee organization, the operational mechanism of mutual credit guarantee has been investigated in this paper. It has been found out that the relativity of guarantee cost saving for SMEs is changing positively with the incentive intensity of mutual credit guarantee to SME; compared with nonmutual credit guarantee, it is beneficial for mutual credit guarantee to raise the incentive intensity and the effort level of SMEs and to save agent cost under asymmetric information.