The effect of efficiency of power dissipation on hot workability and corrosion behavior of AZ31 alloy was investigated. The results indicate that minor Ca-addition can significantly improve the hot workability and corrosion resistance due to grain refinement by facilitating recrystallization and formation of a more protective corrosion product layer doped with a trace amount of Ca(OH)₂. The instability zone exhibits worse corrosion resistance than dynamic recrystallization (DRX) domain due to heterogeneous microstructure and obvious wedge cracks. Moreover, wedge cracks caused by flow localization band can serve as channels for the diffusion of aggressive Cl^- and accelerate further corrosion of Mg matrix. The DRX domain with homogeneous fine grain microstructure and high efficiency of power dissipation obtained by hot deformation at 400 ℃/0.001 s^-1 of Mg-Al-Zn-Mn-Ca alloy simultaneously performs superior corrosion resistance and good hot workability.