Based on the data released by the National Health Commission on the total number of COVID-19 patients and the number of asymptomatic patients from December 12, 2021 to December 12, 2022, this paper discusses the evolving trend of the proportion of asymptomatic patients in the total number of COVID-19 patients. Using the mean multiple point model and binary segmentation method, the Ratio test statistic is introduced and the Block Bootstrap method is used to empirically analyze the fluctuation law of the observed data. The results showed that the proportion of asymptomatic infections in the total number of COVID-19 infections showed a significant upward trend, with high volatility and high jump characteristics. According to the multiple change point location estimation method, the data is divided into five stages. On this basis, the mechanism between the data changes and the types of infected strains, temperature, regional policies and other factors at different stages was explored.