As a high-altitude inland lake, Qinghai Lake's annual change in surface water area is critical for climate change and water cycle in the cold and arid regions. In order to study the spatial and temporal variation of area of Qinghai Lake in the past 30 years, extract 459 images from Landsat 5/8 that covering Qinghai Lake from 1986 to 2017 (excluding 2012). Apply six common water extraction methods to extract the surface water area of ??Qinghai Lake and analyze the differences of methods. Finally, obtain the annual surface water area variation of Qinghai Lake from 1986 to 2017 by using MNDWI and WI2015 water extraction methods for Landsat5 TM and Landsat8 OLI images respectively, and analyze its variation trend. The results show that the area of ??Qinghai Lake decreased by 175.34 km² from 1989 to 2003, and the average annual reduction rate was 12.52 km²/a . The area of ??Qinghai Lake increased by 183.43 km² from 2003 to 2017, and the average annual increase rate was 13.10 km²/a. The area of ??Qinghai Lake increased by 104.46 km², and the average annual increase rate was 3.37 km²/a from 1986 to 2017.