Google Earth (GE) has powerful functions to view landscapes in fairly realistic three dimensions (3D) as well provides digital elevation model (DEM) data. A GE-based method in terrain surveying of debris flow watershed was elaborated, consisting of DEM data and related functions in GE. The method was employed in 9 debris flow watersheds along Ya-lu Expressway, Sichuan, China. It was proved to be able to get a similar result with traditional map method, especially in the debris flow watershed with a large area, such as more than 12 km2. Moreover, the GE method is a time-saving method and can extract some of the terrain parameters directly, which is obviously better than traditional method.