The number of COVID-19 infected persons in Wuhan is estimated by statistically analyzing the ratio of daily confirmed cases number data of COVID-19 in 50 cities in China from January 29, 2020 to February 9, 2020 owing to Wuhan migration. The study finds that the mean and median of diagnosis rate of 15 cities in Hubei Province are lower than that of 35 cities outside Hubei Province. As of February 9, 2020, using the mean, median and maximum values of diagnosis rate in inner cities of Hubei Province, it is estimated that the number of people infected in Wuhan is 2.1 times, 2 times and 3.9 times of those who have been diagnosed, respectively, while using the mean, median and maximum values of the diagnosis rate in cities outside the province, it is estimated that the number of people infected in Wuhan is 3.6 times, 2.6 times and 8.7 times of those who have been diagnosed, respectively. The mean and median of diagnosis rate in cities in and out of Hubei Province are estimated robustly by bootstrap method. © 2020, Editorial Board of Journal of the University of Electronic Science and Technology of China. All right reserved.