In recent years, against the backdrop of RMB internationalization and capital flow control, the Chinese government has had a pressing need to continuously promote the opening of the capital market. The most important capital market opening in China in recent years is the opening of the Shanghai-Hong Kong Stock Connect in 2014 and the Shenzhen-Hong Kong Stock Connect in 2016. The implementation of the Shanghai-Shenzhen-Hong Kong Stock Connect trading system marks a new stage in the opening up of China's capital market. How will the opening of the capital market affect corporate behavior and decision-making? Mergers and acquisitions (M&A), as a form of large-scale corporate investment behavior, plays a crucial role in the long-term development of enterprises and the optimal allocation of resources. It has also been a hot topic in academic literature in recent years Therefore, under the background of capital market opening, how will the Shanghai-Hong Kong Stock Connect and the Shenzhen-Hong Kong Stock Connect affect M&A activities of Chinese enterprises? With this question in mind, this paper uses a sample of A-share listed companies in China to analyze the impact of capital market opening on corporate M&A.