Study on the response of vegetation to altitude gradient is helpful for us to understand how alpine ecosystems will response to future climate change. We chose to study the vegetation along the south slope of the Nyenchentanglha Mountain, with the altitude gradient from 4 775 m to 5 305 m. Along the altitude gradient, samples were set every 30 meters and species, with plant height, coverage and species frequency investigated in each samples. Double gaps indicator species analysis (TWINSPAN), and Detrended correspondence analysis (DCA) were applied to analysis the community types and species diversity along the altitude gradient of the southeast slope of the Nyenchentanglha Mountain. TWINSPAN divided the plant communication into 5 types:Sabina pingii var. wilsonii + Kobresia pygmaea meadow community, Kobresia pygmaea + Polygonum macrophyllum meadow community, Kobresia pygmaea + Kobresia humilis meadow community, Kobresia pygmaea community and stone beach periglacial vegetation communities. The result of vegetations classification by TWINSPAN reflected the relation between communitys location, topography and altitude, which were verified in pattern map of DCA very well. The species was lower in high and low altitude area compared with the middle of slope of mountain, which formed a hump cure. The species diversity index from high to low of community was herb layer >shrub layer > periglacial stone-community. The model of diversity index and altitude was negatively quadratic function.