Powdery mildew is an important parasitic fungus of higher plants widely distributed all over the world. It can cause disease in many plants and harm a variety of economic plants in the result of serious losses. From September 2008 to May 2019, the powdery mildew on woody plants in Liangshan Yi Autonomous Prefecture has been studied. A total of more than 50 species of 6 genera are identified, and 8 of them are reported as common and hazardous: Erysiphe pileae (Jacz.) Bunk ex Braun, Neoerysiphe galii (S.Blumer) U.Braun, Erysiphe sikkimensis Chona, J.N. Kapoor & H.S. Gill, Erysiphe aquilegiae var. ranunculi (Crev) (Grev.) R.Y. Zheng & G.Q. Chen, Erysiphe hommae (U. Braun) U. Braun & S. Takam. 2000, Microsphaera robiniae Tai, Uncinula kusanoi Syd. & P. Syd, and Pleochaeta shiraiana (Henn.) Kimbr. & Korf.