The spatiotemporal variations and influencing factors of erosion gully in the last 50 years in Wangmaogou Watershed were studied by extracting some information like shoulder line, land use, soil and water conservation measures, vegetation coverage and LS from the three high-resolution remote sensing images of 1968, 2004 and 2018. The results showed that:(1) The information collected by remote sensing could basically satisfy the analysis of medium and long-term change in the erosion gully. (2) Gully erosion in Wangmaogou Watershed was developing all the time, but this change tempered gradually in the past 50 years. Specifically, the average advance rate of gully head were 0.30 m/a and 0.27 m/a respectively in early stage and the late stage, and the average expansion rate of gully wall were 0.009 m/a and 0.004 m/a. Spatially, the proportion of the variation density of erosion gully above 200 m/(km²·a) in the two periods were 26.89% and 7.07% respectively, which mainly distributed in the middle and lower reaches of the watershed. (3) In 1968-2004, the dominant factors affecting the development of erosion gully were land use changes and increased soil and water conservation measures, while erosion gully changes were mainly affected by the further improvement of vegetation coverage and land use diversity in 2005-2018. The study could help to quantify and analyze the development of erosion gully and its influencing factors for many years in the management process, and could also provide an important reference for ecological benefit evaluation of erosion gully before and after the implementation of "Grain-for-Green Program".