Abstract: In this paper, we provide a statistical analysis of population movements leaving Wuhan based on mass population movement information which is collected by geographic services of Tencent and Baidu. Firstly, we find that the five million people leaving Wuhan before the official announcement that they will close the exits are not much different from the normal population movement during the previous Spring Festival travel rush. However, small portion of the population poured out of Wuhan in the last period before the exits closed. Secondly, according to statistics of the destination cities of the outflow population from Wuhan starting from 2020, we find that the destination distribution of folks in 2020 was basically same as that in previous years. Finally, the influence of the population leaving Wuhan on epidemic spread is analyzed. We find that the role of incubation period must be considered when measuring this influence. This study is helpful for relevant personnel to grasp the speed of epidemic spread, assess the risk of epidemic, and provides reference to predict and stop disease spreading.