The Fintech are characterized by rapid update and iteration, crossover, and mixed industry. It is the superposition and integration of big data, artificial intelligence, blockchain technology and other cutting-edge disruptive technologies with traditional financial businesses and scenarios. It mainly includes four core parts: big data finance, artificial intelligence finance, blockchain finance and quantitative finance.In recent years, the rapid development of financial technology has brought advanced technology to commercial banks, accelerated the pace of reform of commercial banks, and also brought a severe test to the traditional business model of commercial banks. On the positive side, commercial banks have received new technical support. The application of financial technology has greatly optimized the traditional business model of commercial banks, simplified the business process of banks, and promoted the development of banks in the direction of digitalization. On the negative side, fintech and the traditional business of banks produce interactive competition and running in, and the uncertainty of the original market share of banks is strengthened. Therefore, facing the "double-edged sword" of financial science and technology, how commercial banks should respond, and how to expand customer channels, improve profitability, and achieve transformation and upgrading with the help of the dividends of financial science and technology development become the top priority. Based on the relevant theoretical research, this paper combs the specific impact mechanism from both positive and negative aspects, and then uses the data of 22 commercial banks from 2011 to 2020 to analyze the mechanism of financial technology affecting the profitability of commercial banks through systematic GMM.