The kiangs (Asinus kiang) is a unique species on the Qinghai-Tibet Plateau and the first-class protected wild animal in China. The Yellow-River-Resource Park of Sanjiangyuan National Park is one of the main habitats of kiangs, and biodiversity protection is one of its basic function. Thus, it is of great significance to accurately know the population and habitat change of kiangs not only from the perspective of wildlife protection but also from the guidance of national park construction. In this study, the Yellow-River-Resource National Park was chosen as the study area, and unmanned aerial vehicle (UAV) remote sensing technology was used to carry out the population survey of kiangs. Furthermore, the line transects sampling method which is usually used for ground investigations was carried out in this study for the estimation of kiangs' population, and the selection index and factor analysis were used to reveal the habitat selection preference of the kiangs and their suitable habitat range was identified. The spatial and temporal variation characteristics of suitable habitat of kiangs in the past 20 years as well as the driving factors were discussed. Results showed that:(1) the individual kiangs could be effectively identified in UAV images with a spatial resolution of 4-7 cm. A total of 252 kiangs were found in the survey transection. It was estimated that there were 20989 kiangs in the Yellow-River-Resource National Park in spring 2017. (2) The kiangs preferred flat areas with slope less than 5° and vegetation coverage between 0.4 and 0.8, which were 1 km away from settlements, 1-3 km away from roads and 1 km within water. (3) From 2000 to 2018, the area of suitable habitat for kiangs in the Yellow-River-Resource Park of Sanjiangyuan National Park increased 330.76 km² and reached 4747.10 km² in total, the proportion increased from 23.12% to 24.85%. This was mainly driven by the expansion of water body and the increase of vegetation coverage caused by the synergistic effect of climate change and human activities. In addition, although road expansion only limited the increase of suitable habitat in small areas, it might have more serious consequences, such as reduced habitat connectivity. This study proved the feasibility and advantages of UAV remote sensing technology for wildlife investigation and habitat research in open areas such as the Qinghai-Tibet Plateau. The relevant technologies, methods and research results can provide reference and support for biodiversity protection in Sanjiangyuan National Park.