Abstract: By twodimension gel electrophoresis, differential proteomic analysis was conducted on Populus beijingensis(sensitive to Botryosphaeria dothidea) and P. tomentosa(resist to B. dothidea) before and after inoculated with B. dothidea（2DE）. Comparison of the 2DE maps of proteins from the two inoculated and control species. The results showed that 35 3fold different proteins were detected between the two species.Among which there were 4 upregulated proteins, 15 downregulated proteins before inoculation, and 7 upregulated proteins, 9 downregulated proteins after inoculation. For P. tomentosa, there were 8 upregulated proteins and 6 downregulated proteins detected after inoculation, and for P. beijingensis, 8 upregulated proteins and 10 downregulated proteins were identified after inoculation The analysis was taken on the produce conditions and contents of these proteins.It could be deduced that the upregulated proteins expressed in P. tomentosa before and after inoculation may be associated with consistutive resistance mechanisms and induced resistance mechanisms respectively. Four of them were detected by mass spectrometry, which were ribulose bisphosphate carboxylase small clain, predicted protein, superoxide dismutase, isopentenyldiphosphate deltaisomerase respectively. These proteins may be associated with the resistance of poplar to canken.