It is crucial to find the fair value of financial assets for asset pricing model in relevant research and practice. With continuous improvement of the model, researchers are expected to improve the applicability and interpretation ability. Covid-19 is a rare global epidemic disease in human history, causing large-scale negative impact on the financial market. Therefore, it is necessary to study the practicability of asset pricing model, facing major and unpredictable factors. Based on the Fama French five-factor model, this paper compares the model factors of American manufacturing stocks from July 2019 to February 2020, and March 2020 to October 2020. The data mentioned in this paper are all selected from the database of Kenneth R. French's web. French, using the relevant information of American stock market to get various data. Multiple linear regression method and t-test are applied to analyze. The results showed that intercept investment. The asset pricing model changed from non-significant before the epidemic to significant; SMB coefficient is significant both before and after the epidemic, while coefficient increases after the epidemic; RMW is significant before the epidemic and is non-significant after the epidemic; MKT coefficient is significant both before and after the epidemic; CMA is non-significant both before and after the epidemic. Investors are advised to focus more on the explanatory power of MKT, SMB and HML factors on asset pricing when investing on US manufacturing stocks during the epidemic.