Abstract: With the prosperity of population and economy,the ecosystem has been changed greatly in Sanjiang plain in the past fifty years,especially the transformation of the vegetation is more evident.These transformations have aroused the people’s more attention about the ecosystem of Sanjiang plain.The text analyses the basic reason of the formation about the nature vegetation under the especial climate,water and geography,and analyses the distributing pattern of the nature vegetation according to the terrain and hypsography;the text also introduces respectively the characteristics and transformation of distributing,species structure and existing circumstance in the past fifty years about three nature vegetations: model swamp wetland,the forest and the meadow.The basic driving force is explained from nature and artificiality,and the basic transformation mechanism of the model wetland vegetation under the human influence is set forth.