Abstract: According to Kepler orbit motion,the short distance relative dynamics equations of spacecrafts were obtained in the inertial frame.Compared with Clohessy-Wiltshire(C-W) equations,these equations were adaptable to the spacecrafts on the elliptical orbit because of no restriction for eccentricity.To avoid the Taylor linearization,the divided difference 2(DD2) filtering used polynomial interpolation to parameterize the first two moments of a probability distribution.For the determination of the spacecrafts relative position and relative velocity,the DD2 filtering was more accurate and easier to implement than the extended Kalman filtering(EKF).The simulation results validate the availability of the relative navigation algorithm based on DD2 filtering.