Abstract
During the period of different changes in the global situation, the stock indexes of China, the United States and the United Kingdom all showed different trends. Overall, during the outbreak of the epidemic, they all received a huge impact, and due to the different policies and coping strategies of various countries, the follow-up performance also varies greatly. Brexit has only had a slight impact on the British domestic market in a short period time, and China and the United States have prepared for investment in the new market after Brexit, which has also caused the corresponding market index to perform better before the follow-up. Due to the differences in the main market targets and the differences in the geographical location of countries, the negative impact on the British market was more obvious during the Russia-Ukraine conflict, while the stock indexes of China and the United States were relatively stable and even showed an upward trend. It can be seen from the data analysis that the markets in different countries are affected by time differently. With the growing correlation between the markets of various countries, investors should pay more attention to the global situation and the policy orientation of different countries. Considering risk diversification while taking policy dividends helps to obtain stable returns.