Abstract: Through investigating the poplar canker disease in north of Jiangsu, four kinds of symptoms on the poplar canker disease, i. e. blister, small circinal blotch, hlack blotch and hark rot, were found. The big black blotch canker was the most serious one among these cankers. The study on the virulence of three pathogens of cankers to the poplar was carried out. The results showed that there were significant differences in virulence among different pathogens to different poplars. The virulenees of Cytospora ctzrysosperma to poplar NL895(Populus X euramericana cv) aud 1-72(P. euramericana cv. 1-72/58) was greater than that of Phomopsis macrospora and Fusicoccum aescali. The virulences of P. macrospora and F. aesculi to poplar NL895and I-72were similar, while the virulences of three pathogens to poplar 1-69(P. deltoides ev. I-69/55) were similar.