Abstract: A coupling microstructure evolution model of a factory seamless tube stretch reducing mill group during the process of hot deformation was established based on the process specification. A multi-parameter coupled model for the numerical analysis of the thermal, mechanical and microstructure of a seamless tube stretch reducing process was established using a nonlinear finite element method. The rolling process of a 10-stand actual stretch reducing process was simulated using this model. The variation of the tube wall thickness and the evolutions of deformation, temperature and microstructure were analyzed. Moreover, the simulated ferrite gain sizes were compared with the measured ones. The research was helpful for studying the metal microstructure evolution of a stretch reducing process and for predicting the dimensional accuracy of a final product.