Gully erosion holds an important position in soil erosion, and monitoring the gully erosion is the major part of the study of gully erosion. Photogrammetry is mostly used in the study of monitoring gully erosion cur- rently, however, the method has limitations to some extent. This article the study of gully erosion using GPS was discussed by surveying the gully at different time, constructing the DEMs, and comparing the DEMs, the changes of the gully can be obtained. At the last part of the article, a case study of a gully at Fengchan Catch- ment, Heilongjiang Province is presented, the DEMs with resolution of 0. 4 m were constructed, and the dynamic changes of the gully between October 2002 and October 2003 were obtained, it shows that the gully retreated 13. 78 m, the erosion area expanded 711 m~2, and the erosion volume was 2 377 m~3. The case study exposes the ad- vantages of GPS survey in monitoring the gully erosion, and provides an alternative approach to monitoring the gully erosion.