Abstract: The differential VLBI model used for Lunar probe positioning is derived.CE-1's data is used to estimating ERP as well as positioning.The results show that:① The ERP's precision has a great influence to the probe positioning accuracy,and the increasing of ERP accuracy can help to improve the positioning accuracy of the probe.② The ERP's precision can be improved by estimating probe's position and ERP parameters simultaneously with the ΔDOR observations between the CE-1 Lunar probe and a reference radio source.