Based on the SME loan data of a national rural bank, this paper makes a comprehensive analysis on the factors influencing loan default. The results show that, among the loan characteristics, revolving loan, multiple loans, lump-sum repayment of principal, loans for fixed assets and operating turnover have significant negative impact on default, while guarantee company's guarantee, contract amount, loan term and loan interest rate have significant positive impact on default. Among the characteristics of SMEs, large annual sales, agriculture and manufacturing industries will significantly increase the probability of default. In terms of regional characteristics, firms located in the eastern and central regions and regional GDP growth are significantly negatively correlated with default. These findings provide some references for banks to identify the credit risks of SMEs and for SMEs to optimize the financing process.