The vigorous development of fintech has provided new ideas for commercial banks to improve financial services for small and micro enterprises (SMEs). The paper uses data from a nationwide survey questionnaire on SMEs credit in commercial banks as a sample to explore the impact and mechanism of fintech on precision credit for SMEs. At the same time, it further studies the moderating effect of credit supervision environment in this process. The results indicate that fintech can significantly improve the accuracy of credit for SMEs, and this path can be achieved by weakening information distance constraints and improving customer infrastructure. Heterogeneity analysis shows that large commercial banks have more advantages than small and medium-sized commercial banks in improving the accuracy of credit for SMEs. The credit capacity of SMEs in the western and northeastern regions has greater potential for improvement compared to the eastern and central regions. In addition, in areas with poor credit regulatory environments, fintech plays a greater role in improving precision credit. The paper enriches the theoretical explanation that fintech improves credit for SMEs, and also provides management inspiration for commercial banks to enhance their financial service capabilities for SMEs.