Abstract: The hot compression test of WE43 magnesium alloy at deformation temperature of 300-500 ℃ and strain rate of 0.000 5-0.5 s^-1 was carried out on Gleeble 3800 numerical control thermo-mechanical physical simulator, and the hot deformation behavior of the alloy was investigated. The processing map at strain of 0.6 was established, and the optimum hot working parameter range for WE43 magnesium alloy was determined by combination with microstructure evolution. The results show that the true stress of WE43 magnesium alloy increased with decreasing deformation temperature or increasing strain rate, and the true strain corresponding to the peak stress decreased with decreaseing strain rate or increasing deformation temperature. The optimum thermoplastic working ranges for WE43 magnesium alloy were deformation temperature of 410-500 ℃ and strain rate of 0.05-0.005 s^-1; at the same time, the hot deformation softening mechanism of the alloy was mainly dynamic recrystallization, and the grain size was relatively uniform with average grain size of less than 100 μm.