The Japanese government arranged a total of three charter flights to evacuate Japanese residents out of Wuhan Jan 29, 30, and 31, 2020. The project to rescue Japanese residents can be recognized as a randomized sampling study for the COVID-19 epidemic in Wuhan at that time. Jan 23, Jonathan MR et al stated in the medRxiv, in 14 days time (Feb 4, 2020), the number of infected people in Wuhan is estimated to be greater than 190 thousand (prediction interval, 132,751 to 273,649). In our study, the estimation of the COVID-19 cases in Wuhan around Jan 29, 30 and 31, 2020 exceeds the lower prediction 132,751 in the prior probability: 0.0134. Our statistical analysis is consistent with Jonathan MR et al, if the specificity of SARS-CoV-2 PCR assays in Japan exceeds 99.7%.