The effect of aging treatment on microstructure and mechanical properties of forging heat鄄resisting Mg alloy was studied by single aging treatment. The aging phase and fracture behavior were analized. Accroding to the ex鄄 periment results the optimized treatment process and intrinsic mechanism were achived. After heat treatment at 200益伊 63 h,the fracture strength reaches 371 MPa, the yield strength reaches 243 MPa and the elongation reaches 4.1%.