Abstract: Cottonwood clone 69, clone 72, and Simon poplar, were inoculated with 12 ectomycorrhizal fungi, respectively. Experiment results indicated that Lactarius insulsus and Xerocomus chrysenteron were elite ectomycorrhizal fungi, which led more than 50% ectomycorrhizal infection and evidently promoted seedling height of the tested three poplars. We also inoculated cottonwood clone 895 with 6 ectomycorrhizal fungi. It was found that Xerocomus chrysenteron, Lactarius insulsus and Boletus edulis accelerated seedlings generation from cuttings of clone 895 more than the other fungi did, and they remarkably promoted seedling growth comparing with the control. Lactarius insulsus promoted aboveground biomass and root system most effectively. All kinds of ectomycorrhizal fungi formed mycorrhizal mantle and hartig net structure. These fungi facilitated the fine root germination, and enhanced growth increment of root system.