Abstract: In this paper,the possibility and data processing techniques for error analysis of tracking data and for radar precision judgement by the using difference GPS method are discussing.Assuming that there are a GPS signal receiver mounted in a radar station and a GPS signal transmitter loaded on a rocket,all of the error sources of GPS trackingdata are analysedin detail,and two additive models are built also.Based on two kinds of difference GPS algorillms suggested in this paper,a high precision location algorithm of carrier rocket is deduced.In order to separate all of the systemtic error residuals from total error and to analyse stochastic error of radar measuring data,a new and more essential concept “biasness”is advised,and a series of practical algorithms about stationary test are developed.When the indirect difference series are stationary,two rlbustresistant statistics are given to estimate the fixed bias errors If there exists any trendency error in the indirect difference,the best separation method and the resistant algorillm of residual analysis are given also.It can be shown that all of the statistics given in this paper are resistant against any kinds of outlying tracking data.