Fintech brings innovation to business, processes, and products, while it also leads to a reduction of the interest rate. However, the impact of this on business performance of banks has not yet been consistently established. Using text mining methods, an inner fintech development index for 135 banks in China was constructed during 2012 to 2019, the relationship between fintech development and business performance of banks was empirically tested. The results show that the fintech of small banks has no significant impact on business performance during the sample period. After excluding small banks, the impact of fintech on business performance shows a U-shaped relationship with a decreasing trend at first, followed by an increasing trend. Specifically, basic fintech development has no significant impact on business performance of banks, while the applied fintech development has a U-shaped impact on business performance of banks. The development of regional fintech reduces business performance of banks. Mechanism analysis shows that fintech can affect business performance of banks through three paths: cost management, risk control and operational efficiency.