AZ80 magnesium alloys were deformed at different temperature (270°C, 300°Cand 330°C)with different deformation ratio from 10% to 50%. The influence of varying the deformation temperature and ratio on the microstructure and hardness of AZ80 magnesium alloy was studied. The experimental results show that the hardness increased with the increasing of deformation and the hardness is up to the peak value with 40% deformation at 300°C. The microstructure was homogeneous and the grain was refined after hot deformation.The roles of both deformation strengthening and dispersition strengthening were to im prove the mechanical property of AZ80 magnesium alloy.