Abstract:Yunnan is a mountainous plateau which is controlled by tropical monsoon.The whole relief of Yunnan is high in the north and low in the south. Even though the altitude declines with the latitude from north to south, the horizontal differentiation is evident and each zone of vegetation latitudinally distributes over a hundred kilometres. Therefore, it may be cal1ed "horizontal zones of the mountainous plateaus type".The major zonal vegetation changes from the south to north as follows:tropical rain forest and monsoon forest -molisoon evergreen broad-leaf forest in southern part of subtropical zone - semi-humid evergreen broad-leaf forest in northern part of subtropica1 zone. Each of these vegetations are distributed in the basin of plateau or in the wide valley and the lower slope of the mountains surrounding these basins, where, the level of horizonta1 zones are founded.