Dynamic recrystallization of IN690 super alloy during tube extrusion had been simulated based on Cellular Automata(CA). It had been determined that model of dislocation density and model of reply and model of nucleation and model of grain growth. It had been obtained that grain morphology and distribution and orientation and size during the process of deformation. The results presented that the grain size of the external wall was smaller than that of the middle under the same extrusion ratio. With the increasing of extrusion ratio, the grain size at the same site of the tube decreased. The relative errors of the grain sizes of simulation and experiment were less than 16.6%.