The performance of BeiDou receiver is affected by the carrier acquisition speed and carrier frequency acquisition error. Traditional algorithms have a large amount of calculation when calculating the fine frequency, thus an approach is proposed to find the fine frequency through phase relation. Firstly, the algorithm uses the FFT circular correlation to realize the fast acquisition. Then the phase relation of the continuous input signal stripped C/A code in a shorter time is used to estimate the fine frequency. The simulation results show that the algorithm can reduce the Doppler estimation error. According to the analysis, when the input signal is strong, the algorithm can keep the error of the Doppler frequency within 10 Hz. When the input signal is weak, it can keep the error of the Doppler frequency within 50 Hz. The study has certain reference value for research on BeiDou receiver.