Siberian crane (Leucogeranus Leucogeranus) was listed as class I national key protected wildlife and the only Critically Endangered (CR) species of cranes. Its distribution and population are important parameters to assess the threatened status of the species. Unmanned Aerial Vehicle (UAV) survey has been an important method for ecological research. To accurately grasp the wintering distribution and population of the critically endangered species, ground monitoring combined with a UAV survey was used to carry out an investigation in the wintering area. The investigation was conducted in lakes and farmlands in Jiangxi, Shandong, Anhui, Hunan, and Hubei Provinces in January, 2022. We used a high-powered telescope for searching and counting cranes in the survey area preliminarily. Then we used micro-UAV at altitude of 100-120 m to take photos or videos of crane groups whose numbers were difficult to count. We identified Siberian cranes and Siberian crane juveniles in the pictures according to the plumage and shape. We calculated the number of Siberian cranes, and the ratios of Siberian crane juveniles in each survey area. We also searched for the information of distribution and number of Siberian cranes on the Internet outside the survey area. A total of 5616 Siberian cranes were recorded, with 5607 of them recorded by field survey, and 9 of them recorded on Internet information. There were 4813 Siberian cranes wintering in Poyang Lake, Jiangxi Province, accounting for 85.7% of the total, mainly distributed in Kangshan farmlands, Wuxing farmlands, and Chengxin farmlands. 625 Siberian cranes were wintering in the Yellow River Delta, Shandong Province, accounting for 11.1% of the total, and 34, 63, and 72 Siberian cranes wintering in Anhui, Hunan, and Hubei Province, respectively. 674 Siberian crane juveniles were counted among the total of 4680 individuals. The ratio of Siberian crane juveniles was 14.4%. The ratio of Siberian crane juveniles in Hunan was the highest, accounting for 28.6%, and that in Shandong was the lowest, accounting for 11.5%. The numbers of Siberian cranes updated by our survey. Based on our research, we estimated that the population of Siberian cranes had reached 5500, and the number of mature individuals had reached 3000. The threatened status of this species needs a more detailed assessment. Our research confirmed that the Yellow River Delta was the most crucial wintering area except Poyang Lake. The numbers of Siberian cranes were more than 10% of the total, which dispersed the wintering individuals and alleviated the pressure of individuals' excessive concentration in wintering area. Our research also provided a case for the application of a UAV survey on waterbird monitoring research.