Abstract: Aiming at the inter-satellite observation pretreatment, this paper describes the epoch naturalization and two-way distance naturalization processing methods. And the efficiency of the algorithm is evaluated using simulated inter-satellite observation. Several error sources which influences the accuracy of naturalization are analyzed. And this paper points out that the interpolation order and sampling interval of inter-satellite observation are the main factors which influence the naturalization precision of inter-satellite links with satellites pointed at different orbit plane.