Satellite coherent optical communication has reached the engineering application stage at abroad, and the mostly used modulation and demodulation technique are BPSK/homodyne detection, in which OPLL is used for carrier recovery. Even nowadays, the application of OPLL is still difficult and the OPLL takes long time to capture the received signal. The open-loop conpensation algorithm based on DSP used in fiber communication was proposed to estimate the frequency and phase, and then was applied to the satellite laser communications. The effect of laser noise and receiver noise on frequency estimation precision was studied emphaisitly, and simulation was implemented to verify the algorithm. Results show that when the power of local oscillator (LO) is 10 dBm, the BER of the system is better than 10-4 with received power higher than -47 dBm; when the received power is increased by 10 dB, the standard deviation of the frequency estimation is less than 370 kHz.