The plant community in the upper reaches of Heihe River in the Qilian Mountains was studied to see how it changes with altitude. Different types of vegetation were found on shallow mountainous areas, shady slopes, and sunny slopes. Shady slopes have mountain desert, mountain forest, and alpine shrub vegetation, depending on altitude. Sunny slopes have dry and wet vegetation types. The diversity of tree species doesn't follow a clear pattern with altitude, but shrub species richness peaks at certain altitudes. The diversity of herbaceous plants peaks at a single altitude. The main tree species, Picea crassifolia, is most common on shady slopes between 2,500m and 3,500m, with less dense canopies at higher altitudes.