Abstract: The black blotch canker of poplars which is a new kind of poplar canker disease occurred in north Jiangsu recently. Research on this disease indicated that it was the main death reason of new planted poplars in this area. According to isolation and identification results, this disease could be caused by Fusicoccum aesculi and Phomopsis macrospora. For F. aesculi, the conidium is single, fusiform and the base truncation. Its size is between (17.5--27.5)μm × (4.0--5.5) μm and the average size is 23.5 μm × 4. 5μm. The conidiospores are transparent, which are branching near the bases. Its average size is 21μm～2.0 μm for P. macrospora, two shapes of conidia are found, i.e. fusiform and linear with curved top. Two pathogens which inoculated the stem of the poplars respectively, caused poplar to have little black spots. The mixed inoculation with two pathogens could aggravate the diseases by forming big black blotch.