Water erosion processes are the focus of soil erosion research driven by disciplinary development and social demands. By summarizing and analyzing the studies of water erosion, this paper discussed: (1) the concept and study methods of water erosion;(2) the main content and achievements of water erosion processes studies, mainly including detachment-transport-deposition on hillslope, erosion-transport-accumulation in watersheds, and water erosion models. Finally, research challenges and future directions were also provided, including water erosion mechanisms, multi-scale features of water erosion, and the mechanisms of soil and water conservation practices.