In December 2019, the Corona Virus Disease 2019 (COVID-19) outbreak occurred in Wuhan, Hubei Province, and spread rapidly across the country in January 2020. The COVID-19 epidemic has brought a certain degree of negative impact on Chinese social and economic development. From the perspective of financial markets, the reaction has been even more dramatic. This article will use the event research method combined with multiple regression analysis to analyze the stock return rate of the Chinese stock market from January to March, and explore the negative effects of this sudden public event on the stock market in China.