Effects of different rolling temperature,different rolling reduction on microstructure and properties of AZ31 magnesium alloy sheet,which was prepared by unidirectional rolling,were investigated.The results reveal that in the condition of multi-rolling,the prepared AZ31 magnesium alloy sheet with uniform and fine grain with average grain size of 6μm can be observed with rolling at 400℃ and one-passes reduction of 25% after heat treatment,and average grain size of 10 μm in the sheet can be observed with rolling at 400 ℃ and one-pass reduction of 35%.During annealing treatment after rolling,incomplete recrystallization occurs in the sheet at temperature below 150 ℃ and holding for 30 min,and average grain size in the sheet can reach 5 μm after heat treatment at 250～300 ℃,while recrystallization structure becomes coarse with disappearance of twins in the rolled sheet after heat treatment more than 350 ℃.In addition,recrystallization occurs in the rolled sheet after heat treatment at 320 ℃ for 15 min,meanwhile,microstructure change is independent of the increase of holding time to 120 min.