In this paper,the Mg-3Zn-0.5Y alloy weld in good shape and defect-free was produced by friction stir welding,and the influence of welding parameters on the microstructure and mechanical properties of the welded joint was studied. As a result,when the welding speed is 110 mm/min,the well-formed weldcan be obtained with the rotation rate at 600 ～1300 r/min. The tensile properties of the joints first increase and then decrease in the range. When the rotational speed of 1 100 r/min,the well-formed weld can be obtained with the rotation rate at 90～1 300 mm/min. With the increase of rotating speed,the joint strength increases first and then decreases. Brittle fracture and ductile fracture can be observed simultaneously. Good comprehensive mechanical properties can be obtained when the rotation rate was 1 100 r/min and the welding speed was 110 mm/min,the tensile strength was 222.5 MPa,the yield strength was 173.8 MPa.