Abstract: Effects of AMF on physiological and biochemical Indexes of tree-peony seedlings were investigated with pot experiment under high temperature stress.Results showed that under the same high temperature,root activity,chlorophyll(a+b) content,proline content,soluble sugar content and soluble protein content of mycorrhizal seedlings were higher and conductivity and MDA content were lower than those of control.With the temperature increasing,the decrease rates of chlorophyll(a+b) content and soluble protein content of mycorrhizal seedlings were lower,the increasing extent of conductivity and MDA content were lower and the increasing extent of proline content and soluble sugar content were higher than those of control.This showed that AMF improved the resisting heat of tree peony.