Abstract: The effects of annealing at different temperatures on the microstructure, mechanical properties and corrosion resistance of hot-rolled Mg-4.0Zn-0.8Zr alloy were studied by metallographic microscope, scanning electron microscope, tensile test and immersion corrosion test.The results show that the grains of hot-rolled Mg-4.0Zn-0.8Zr alloy are elongated along the rolling direction.The microstructure of the alloy annealed at 320 ℃still maintains hot rolled fibrous morphology, and the recrystallization of the alloy annealed at 360 ℃is complete, and the grains are equiaxed.The grain uniformity of the alloy decreases with the increase of annealing temperature.With the increase of annealing temperature, the tensile strength of the alloy decreases, the elongation increases first and then decreases, and the corrosion rate decreases first and then increases.The alloy annealed at 360 ℃has the highest elongation(22.1%), the lowest corrosion rate(0.24 mm/a), and the tensile strength is 250.4 MPa.