Abstract: Influence of temperature on the microstructure and tensile properties of AZ31B magnesium alloy sheet was studied, and the forming quality of hot formed sheet at different temperatures was analyzed. The reasonable hot forming temperature was determined. The microstructure and tensile properties of hot formed parts at the temperature were studied. The results show that AZ31B magnesium alloy sheet could maintain the fine equiaxed structure after heat-treatment at 200 ℃, but the grains were coarsened obviously with the increase of temperature. With the increase of temperature, the strength of the alloy decreased and the plasticity increased. The plasticity and formability were good at 200 ℃. The higher the hot forming temperature, the better the forming quality of the parts. The hot formed parts had good surface quality and smaller spring back deformation at 200 ℃. The ideal hot forming temperature for AZ31B magnesium alloy sheet was 200 ℃. At this temperature, the grains of the parts were refined, and the yield strength and elongation after fracture were improved.