Abstract: Lancang-Mekong River is the sixth largest river basin in the world,its terrain is very complex,with various types of landscape.This paper used spatial analysis with GIS software and mathematical statistics method,based on STRM 90 m×90 m DEM data,to extract the Relief Degree of Land Surface(RDLS) of the Lancang-Mekong River Basin based on grid-scale,and systematic depicted the distribution rules of RDLS in three separate ways:overall characteristics,vertical zones and zonal distribution rules.The research can provide quantitative basis and scientific reference with the whole basin terrain-geomorphologic maps and evaluation of the resources and environment.The result showed that ① The majority of the RDLS is low in Lancang-Mekong River Basin,for more than 63.47% of the area with the RDLS lower than 1 (relative altitude≤500 m).The higher the region’s RDLS is,the lower its proportion of plains is,and vice versa;② As the altitude increasing,the RDLS in Lancang-Mekong River Basin shows gradually increasing,and at the altitude of 3500~3599m and 5 800~5 899 m,there are two peaks,which located in the Hengduan Mountain;③ As the altitude increasing,the RDLS in Lancang-Mekong River Basin shows gradually increasing,and there are five peaks,from south to north,low to high,they are 12°N,16°N,19°N,25°N,and 29°N,the places where they are located are the following:Cardamom Mountains in Cambodia,southern hilly areas of Annan Mountains,north-central areas of Annan Mountains in Laos,the interchange of middle and southern section of the Lancang River Basin,south-east corner of the Hengduan Mountain area in Tibet.