Abstract: The microstructure and properties of AZ31 magnesium alloy sheets containing Y element after annealing were studied.The results indicate that the grain size of the magnesium alloy gradually increases with the increase of annealing temperature,but the mechanical properties slightly increase and then decrease.Annealing time has little effect on the grain size.After annealing at 300℃ for 1h,the magnesium alloy achieves the best mechanical properties,with a tensile strength of 255 MPa,a yield strength of 175 MPa,and an elongation of 24%.The fracture mode of the magnesium alloy is quasi-cleavage fracture and ductile fracture after heat treatment.