Based on the characteristics of MPM deformation process,a thermal-mechanical coupled model of this process was established by the three-dimensional elastic-plastic finite element method.Some important parameters such as the rolled product size in each stand,the temperature variation curves of the key nodes on the tube,the rolling force and torque of each roller,and the equivalent stress and strain of the tube were analyzed using this model.The analysis results are as follows: The external diameter and wall thickness are alternate reduced between the pass bottom position and the roll gap position and tend gradually to finished size; The temperature of nodes,contacting with mandrel or rolls,decrease for heat transfer between tube and mandrel,tube and rolls,rube and surroundings,while the temperature of internal nodes increase for plastic work and decrease following for conduction within tube; The flow law of metal is that the metal in the bottom of pass is radial compressed,and flow towards the roll gap position or along the axial direction.Comparison between simulation solutions and experiment results shows a good agreement,which means that this model is capable of simulation MPM deformation process as well as forecasting product quality.