Abstract: Based on the theory of variation equation,precise low satellite orbit and Earth gravity field model can be determined by using numerical integration technology.Feasibilities and requirements of the algorithm are analyzed by numerical evaluation.Using CHAMP real orbit data,some calculations were performed for studying the influence of initial orbit vectors precise,the force model,and force model parameters errors.The results show that the error of initial orbit vectors and force model parameters are the critical factors and have a great influence on satellite orbit shapes,especially numerical integration is highly sensitivity to initial orbit vector errors.