After investigating the ectomycorrhiza of 35 species of poplars in Shaanxi Province, 9 species of ectomycorrhizal fung were identified. Experimental results proved that a species of ectomycorrhizal fungus can infect different species of poplars, and that a species of poplar can be infected by different species of fungi. It was also discovered that in the same small root mantle was formed on the top, and vesicular-arbuscular was formed on the middle and lower parts. This is a special form of mix-mycorrhiza.