Abstract: The Chang' e-4 mission will explore the back of the moon by the lander,inspector and relay satellites that orbit the second Lagrange point(L2). The relay satellites have been launched and entered Halo orbit around L2 successfully. Based on the mission orbit dynamics model of the relay satellite,the perturbation source magnitude of the relay satellite in Halo orbit and the main factors affecting the orbit determination and prediction are analyzed by simulation. The results show that the Solar pressure perturbation is the main factor affecting the orbit determination and prediction. In order to reduce the influence and improve the orbit determination accuracy,a method for calculating the equivalent pressure area is proposed based on the cannon-ball model,combined with the operational characteristics in orbit and the characteristics of the structure of the relay satellite. The simulation results show that the orbit determination accuracy of velocity can be improved about one order of magnitude by using the modified cannon-ball model