Is There a “Bubble” Behavior in the Daily Newly Confirmed Cases of COVID-19 in China?

To reveal the development trend of COVID-19 in China, the daily newly confirmed cases from January 3, 2020 to December 31, 2020 were selected as the sample. Descriptive statistical analysis and right recursive supremum augmented dickey fuller test were used to analyze the changing trend and detect the existence of "bubble" behavior with the newly confirmed cases. The results show that at the initial stage of the epidemic, the number of daily newly confirmed cases exhibits an explosive development, but after March 2020, the epidemic enters a cyclical fluctuation with low level. The daily new confirmed cases exist several significant "bubble" behaviors with two different cycle, including 12 d and 8 d respectively for a long period as well as 2 d and 1 d respectively for a short cycle, which further verifies the sequence has obvious fluctuation cycle. In view of the current epidemic situation and the law of bubble cycle evolution, it is thought that the epidemic situation is likely to appear a new wave cycle in the future.