Abstract: GPS code pseudorange positioning is not affected no matter whether the reference clocks of RF and baseband are from the same oscillator or not. However, for carrier phase smoothing code pseudorange positioning, theoretical analysis in this paper shows that as some new satellites become visible, a clock bias difference between the new and old satellites’ smoothed pseudoranges occurs, due to different oscillators used by RF and baseband, and it leads to a considerable positioning error. Under the conditions of the same oscillator and two different oscillators used by RF and baseband, sufficient hardware experiments have been carried out by using the self-developed GPS baseband chip HangXin 2E. The correctness of the theoretical analysis has been verified by the experiment results. In this paper, the conclusion that the reference clocks of RF and baseband must be from the same oscillator makes a guidance sense for planning and design of modularization and serialization of GPS RF and baseband chip.