The geometric models and finite element models of triscrew extruder with different rotors have been established, and the models have been simulated by Polyflow. The mixing index, shear rate, logarithm of stretching, instantaneous efficiency, the average time efficiency and other evaluation parameters have been calculated using particle tracking method. The results show that, the number of shear and stretching in triscrew extruder in the same period increase with the increase of screw head numbers. Accordingly, the mixing effect is also increased gradually.