Abstract: Field work should be mapped for soil erosion survey in the first water conservancy survey of China, but the coordinate systems used for field support maps, remote imagery and GPS were different.So it has to be transformed from Xi爷an 1980 into WGS-1984 in order to facilitate the investigation. In this study, 61 sites were chosen for 14 parts in 10 provinces. Three parameters for transforming coordinate system from Xi爷an-1980 into WGS-1984 were estimated by using coord software for every part and then averaged for both regional and national scales. Under the support of ArcMap software, 61 sites in Xi’an-1980 coordinate system were transformed into WGS-1984, and their geographic errors were estimated by comparing the transformed WGS-1984 and google earth image coordinate system. The results showed that both longitudinal and latitudinal errors in average were less than 10 m using regional three parameters,and less than 15 m using national three parameters, which could satisfy the precision of 20 m for national soil erosion survey and could provide convenience for other similar surveys of the country or regions.