Abstract: Wood structure of poplar ( Populus×euramericana ) selected from healthy and acid rain damaged froests was analyzed to evaluate the effects of acid rain on wood properties. Ring width and sapwood width of diseased poplar decreased significantly than that of healthy poplar, but sapwood portion was same. Vessel is known to be sensitive to acid rain, its tangential diameter of diseased poplar decreased than that of healthy poplar. The significant difference of fiber width between diseased and healthy poplar led to the significant difference of ratio of fiber length to fiber width. The variation of microstructure of diseased poplar wood, i.e. false annual ring, double annual ring, variation of vessel section, rise of tylosis in vessel, parenchyma fiber and split, were observed by image analysis system and scan electron microscope.