Under the wave of digital economy, China's banking industry is accelerating the pace of digital transformation. So how will digital transformation affect the profitability of China's banking sector? Based on the digital transformation panel data of Chinese listed commercial banks, the impact of digital transformation on the profitability of commercial banks was examined. The results show that under the severe situation of banks' profitability space being continuously compressed, carrying out digital transformation can significantly reduce banks' operating costs, improve the degree of bank diversification and operational efficiency, and then improve their profitability. At the same time, the impact of digital transformation on bank profitability is characterized by structural heterogeneity. The effect of digital transformation on the profitability of large-scale banks is more obvious. Big data technology transformation has a greater impact on bank profitability, followed closely by blockchain, artificial intelligence and cloud computing technology. Further research finds that a rise in both bank innovation ability and industry concentration undermines the promotion effect of digital transformation on bank profitability. It can provide useful lessons to better drive banks' digital transformation and improve their profitability.