Abstract: We have done some analysis about the effects of two separate oscillators in RF and in baseband on carrier-phase measuring.And we propose a model for the error of carrier-tracking loop,which is based on all kinds of oscillator's error sources.The analysis and experimental results show that two different clock sources could result in carrier phase measurement error,and the carrier-tracking loop measurement error caused by oscillator could be reduced by increasing the loop noise bandwidth.Moreover,that measurement accuracy can also be advanced by reducing h-factor and g-sensitivity.Additionally,the measurement quality of carrier phase could be improved by adopting a single highly stable and low g-sensitivity oscillator in choosing the GNSS receiver clock.