Abstract: The study on the penetration of interplanetary energetic particles into the magnetosphere, is one of the key problems in magnetospheric and space weather study. Most of the previous works concentrated on the statistical investigation of the penetration of energetic particles into magnetosphere under different interplanetary conditions. In this paper, the new-developed code is used to calculate the trajectories of energetic particles' penetration into the magnetosphere based on T89 model with different energies and pitch angles. The preliminary results show that only those particles moving along the magnetic field lines can penetrate and reach the earth's surface. The particles will be reflected earlier with larger deviation angle with respect to the magnetic field lines. The particles with higher energies can penetrate into the magnetosphere with larger distribution of the pitch angle, but only those with directions along the magnetic field lines can reach the ground. All these results are in consistent with theoretical predictions.