Abstract: By constructing a new New Keynesian DSGE model of credit risk preference of commercial banks, this paper studies the impact of risk preference of commercial banks on credit loan of Small-micro enterprises by incorporating the gap between corporate default and mortgage asset depreciation into the analysis framework. The study found that with the increase in the depreciation of mortgage assets, the threshold for Small-micro enterprises to take risks decreases, the borrowing cost increases, the loan size and leverage ratio decrease, and effective output decreases; As asset risk appetite increases, the elasticity of commercial banks' loan interest rates to Small-micro enterprises decreases, resulting in higher mortgage interest rates, lower borrowing costs, increased loan size and leverage, and increased effective output; The increased preference of commercial banks for default risk of Small-micro enterprises has led to an increase in the elasticity of loan interest rates, a decrease in mortgage interest rates, an increase in borrowing costs, and a decrease in the size and effective output of small and micro enterprise loans.