Abstract: In order to realize the precise tracking of GPS code in the environment of satellite motion,discriminators gain conception is given and the gain forms of the usual discriminator are derived.Then the deduction is given that the larger the discriminator gain is,the higher the pull in speed is and the lower the steady tracking precision is.The effect of correlator space,loop bandwidth and the correlator gain on precise tracking are discussed.The analysis is given that correlator space decrease deduces the tracking error more than dynamic decrease.The correctness of the deduction and the analysis are validated by the Matlab simulation platform.At last,a more reasonable loop design scheme is proposed based on narrow correlator and dot production discriminator.