Compressive properties of AZ31 alloy were investigated at temperatures from room temperature to 543 K and at strain rates from 10-3 to 2×104 s-1. The results show that the compressive behavior and deformation mechanism of AZ31 depend largely on the temperature and strain rate. The flow stress increases with the increase of strain rate at fixed temperature, while decreases with the increase of deformation temperature at fixed strain rate. At low temperature and quasi-static condition, the true stress-true strain curve of AZ31 alloy can be divided into three stages (strain hardening, softening and stabilization) after yielding. However, at high temperature and high strain rate, the AZ31 alloy shows ideal elastic-plastic properties. It is therefore suggested that the change in loading conditions (temperature and strain rate) plays an important role in deformation mechanisms of AZ31 alloy.