Aiming at the biomechanical characteristics of upper leg impactor in the pedestrian protection collision test, THUMS(total human model for safety) model and upper leg impactor were compared and simulated. Firstly, the THUMS-SUV pedestrian accident is simulated, and the impact force and bending moment of THUMS model of upper leg were output. According to the initial condition and minimum energy status of pedestrian upper leg in the accident, two upper leg impactor collision models were established and simulated. The kinematic behavior, maximum bending moment and maximum impact force between THUMS upper leg and upper leg impactor were compared and analyzed. The result showed that the upper leg impactor had higher impact force, but lower bending moment compared to THUMS model. This paper indicates that, due to movement and contact of lower leg and upper body, the contact force and bending moment of upper leg is affected, which means the biofidelity improvement is needed for the upper leg impactor.