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In group formation,the main spacecraft (target) is likely to make suddenly move,all the chasers should have the ability to keep up.Except for radars and cameras as traditional ways,relative navigation between spacecrafts by taking advantage of Global Navigation Satellites System (GNSS) is a method to supply the better precision with the development of navigation systems.However,some of the GNSS constellations can’t be used (such as part of GPS suddenly failure),and the target suddenly moves.In this bad situation,the focus is on whether GNSS be used to acquire the position and velocity information of the target or not and the accuracy meet the requirements or not.The GNSS for the space relative navigation has four working modes: position/velocity,pseudo-range,carrier phase and carrier phase smoothing,the pseudo-range mood is the most common.Pseudo-range differential effects mode is under the largest concern.The state equation and the observation equation is also constructed,the state consists of six parameters,position and velocity each from three directions.The measurement is the pseudo-range.By differencing pseudo-range in a direction,the relative position information can be acquired,the relative velocity information can also be got by Kalman Filter.The accomplishment of simulation is based on the relative navigation soft developed with the Matlab/Simulink.The GNSS is designed to contain three constellations: GPS,GLONASS and COMPASS.The system is derived by the real navigation satellites ephemeris downloaded from the website.The simulation results show the relative position error and relative velocity error between two spacecrafts in the situations of part of GPS is blocked and intact GNSS in the suddenly move.The conclusion can be drawn by comparison that in maneuvering flight,as long as the require number of visible constellations meets four,although a small number of constellations are shielded,the accuracy of navigation do not affect that much.