As a typical representative of the herbivorous wild animals in Chang Tang Plateau, the number of Tibetan wild asses has increased significantly in recent years. Clarifying the distribution, population, and size of its habitats is conducive to formulating the protection plan for wild animals and managing the conflict between people and wild animals in Chang Tang Plateau. Based on the distribution probability of Tibetan wild ass habitats and environmental factors, the number of Tibetan wild asses in Gaize County of Chang Tang Plateau was calculated by using the belt transect method and random forest model, and due to the uncertainty of the calculations, the results were corrected and analyzed. The results show that the living environment of Tibetan wild asses in Gaize County of Chang Tang Plateau is at 4400–4600 m above sea level, 350–400 m away from the river, and the average temperature in the warmest season is 10–12 °C. The vegetation types of habitats are generally temperate tufted dwarf grass, dwarf semi shrub desert grassland, alpine grass, Carex grassland, alpine cushion dwarf semi shrub desert, among others. On the basis of studying the environmental preferences of Tibetan wild asses, the random forest model was corrected by using the data of the second scientific survey sample line of Qinghai-Tibet Plateau for three years. The approximate number of Tibetan wild asses in each of the different areas of Gaize County was obtained. The number of Tibetan wild asses in Gaize Town, Xianqian Township, Gumu Township, Chabu Township, Mami Township, Wuma Township and Dongcuo Township is 855, 3458, 2358, 1453, 743, 943 and 647, respectively. By studying the environmental preferences of Tibetan wild asses and analyzing the results of the belt transect survey, the random forest model can accurately estimate the number of Tibetan wild asses in Gaize County of Chang Tang Plateau.