Abstract: The cushion plant is an ecotype adapted to the environment of the alpine cold climate. There are over 15 species in Northern Xizang plateau, among them Thylaco- spermum caespitosum, Arenaria musciformis and Androsace tapete being common. The general morphology of such plants is expressed as a cushion-like body resulted from the shoots piled up together closely. They may be divided into two types, the close cushion plant and the sparse one, based upon the different degree of compactness of the shoot. The cushion plant is distributed from 4500 to 5300 meters. Different species have different environmental requirement and form the specific community of the alpine cushion vegetation. It has formed in course of the natural selection of the surrounding factors such as plateaus' intense solar radiation, cold weather, strong wind, etc. For a long time, they have sufficiently used the favorabe factors and avoided the unfavorable factors under severe conditions.