Abstract: In order to research canker of Populus × euramericana '74/76', Canker fungus of P.× euramericana '74/76' was isolated in laboratory, inoculated pathogenicity tests were finished in field, and morphological observation and ITS sequences from May 2010 to September 2012.The results showed that Phomopsis vaccinii isolating rate was 68%.Amount of growth of the Phomopsis vaccinii was 0.7 cm in 1 day on PDA medium.Black pycnidia began to product for 5^th days, exuding masses of conidia which were white or with a slight pink tinge after 10 d.Pycnidial stromata surface or semi-surface, black, spherical or irregular shape, single lobular 200-500 μm in diameter on PDA.Conidiophores spindle-shaped or cylindrical, 15-25 μm × 1.2-1.7 μm, 1-3 septa, branched.Conidiogenous cell enteroblastic, phialidic, 10-15 μm × 1-1.5 μm.Conidia of 2 basic types, alpha-conidia 1-cell, hyaline, fusiform, straight, usually biguttulate, 6.9-10.8 μm × 2.1-3.3 μm, average 8.1 μm × 2.8 μm; beta -conidia hyaline, filiform, straight or more often hamate, eguttulate, aseptate, 17.3-24.2 μm × 1.3-1.8 μm, average 20.3 μm × 1.3 μm.1 year poplar seedlings were inoculated in field, incidenced to be 100% after inoculation for 20 d.The pathogenic fungus was identified as Phomopsis vaccinii based on morphological characteristics and ITS sequences.It was the first time to report on Populus × euramericana '74/76', also a new disease on the poplar in China.