Abstract: The Golmud River Basin is located in the southwest of the Qaidam Basin in Qinghai Province, which provides guarantee of water resources for the city of Golmud. The basin is characterized by plateau continental climate, drought, less rain and strong evaporation. Groundwater and surface water are mainly drained by evapotranspiration (ET) in arid inland areas. Therefore, it is of great significance to accurately estimate the temporal and spatial distribution of ET and its influencing factors in the long time series in the study area for the rational development and utilization of water resources and ecological environment protection. However, studies of ET and its influencing factors of the Golmud River Basin have been insufficient for many years. Traditional methods of ET estimation are difficult to obtain temporal and spatial parameters on a large scale and have large errors in estimation results. The valley piedmont plain of the Golmud River Basin is taken as the study area, and a spatial and temporal distribution of time series trends of ET are estimated, so as to provide reference for rational development and utilization of water resources in the study area. Based on the SEBS model, the continuous MODIS data and GLDAS meteorological data are used to estimate the regional ET in this paper. Linear regression method and Mann-Kendall significance test are used to analyze the variation trend of continuous time series. The impact factors of ET are discussed in this work. The results show that the regional ET increased in the Golmud River Basin from 2001 to 2016. The ET value is stable in most areas of the salt marsh and the piedmont gobi gravel plain, whereas it increased in salt lake and oasis plain during the 16 years. The increase and decrease of summer ET is much larger than that of other three seasons, and winter ET has the smallest variation in different geomorphic units.