Abstract: Based on the constitutive relationship of IN690 alloy obtained by isothermal compression,a finite element model of hot extrusion was established for IN690 alloy tubes.In the model the heat conduction between the billet and the die,the convection of heat transfer,and the thermal conversion of plastic work and friction work were taken into account.Simulation results show that the billet temperature starts to rise when the billet approaches toward the deformation zone and increases rapidly when coming into the deformation zone,and the temperature peaks at the die hole's outlet near the mandrel.Besides,the billet temperature around the mandrel is higher than that beside the container.The temperature rise reaches the peak at the end of the filling extrusion stage.The influence of process parameters on the outlet temperature was analyzed.It is indicated that the outlet temperature increases with extrusion speed and reduces seriously when the extrusion speed slows,but the rise of outlet temperature decreases when the preheating temperature of the billet increases.When the friction coefficient is less than 0.04,the friction coefficient has little effect on the outlet temperature,but if the friction coefficient becomes greater than 0.1 the exit temperature will significantly increase.