Abstract: Hot compression experiments of AZ31 magnesium alloy had been carried out at deformation temperature of 200-400℃ and strain rate of 0.01-1 s-1 on a Gleeble-1500D thermal simulator.The hot deformation behavior was investigated and the main deformation characteristic parameters were acquired.Then the mathematical model of high temperature flow stress and the iso-efficiency map were established.The results show that the temperature and strain rate dramatically affected the flow stress during hot compression process of AZ31 magnesium alloy and the stress-strain curves showed an obvious characteristic of dynamic recrystallization.The dynamic recrystallization easily occured with higher temperature and smaller strain rate.And the hot deformation process was controlled by deformation activation energy.The flow stress was expressed by ln=35.74+9.96lnsinh(0.01σ)-1.96×105/RT.The iso-efficiency coefficient increased with the increasing temperature and decreasing strain rate.