The relationship between China and the United States has undergone great changes, from cooperation to competition or even confrontation. It is of great significance to analyze the relationship between them from the perspective of neo-realism. With the deepening of global financial integration and the gradual opening up, the volatility transmission among stock markets in various countries has become more and more obvious. The stock market has become an important part of China's financial system, which is of great significance to improve the efficiency of capital operation and reduce the financing cost of enterprises. And the United States and China have formulated their stock market policies based on neo-realism. The United States needs to face up to China's economic strength and safeguard its interests through global financial hegemony. China needs to face up to the reality and enhance the global financial influence in order to safeguard its stock market.