Credit risk is a result of the loan business of commercial banks. The definition of credit risk, on the one hand, refers to the uncertainty of whether borrowers can keep servicing the loans or not; On the other hand, it refers to the possibility of bank crisis due to the formation of a large number of non-performing loans. Commercial bank is a kind of enterprise which pursuing maximum profit is its ultimate goal. Credit business is the core business of commercial banks, and credit assets account for quite a large proportion of total assets, therefore, the size of the credit risk of a commercial bank has a close relationship with its normal operation.