Abstract: The flow stress evolution law during hot compression of steel AerMet100 was studied by Gleeble-1500D thermo-simulation tester.The results show that the flow stress decreases with increasing hot deformation temperature and increases with enhancing the strain rate and the amount of deformation.The mathematical models of the flow stress evolution with the hot deformation temperature,strain rate and amount of deformation have been established based on the ternary-quadratic regression analysis method.The simulating results agree basically with the experimental ones.