When low-orbit small satellites carry out coherent laser communication, it is necessary to solve the clock deviation problem between the transmitter and the coherent optical receiver in real time. In this paper, the influence of clock deviation on the performance of coherent optical receiver is analyzed, a parallelized clock recovery feedback loop based on Gardner algorithm is designed to correct the clock deviation, and the principle of each component is explained. The algorithm is implemented on FPGA by dividing the 5 GSa/s sampling signals into 32 parallel channels in the FPGA with the main frequency of 156.25 MHz to complete the clock synchronization processing, and the real-time clock synchronization algorithm only occupies 590 adaptive logic blocks and 4 multiplier units of the FPGA. At the same time, the self-developed integrated coherent optical communication module was used to demonstrate the 10 Gb/s PM-QPSK coherent optical communication system experiment. The experimental results show that the scheme can stably compensate the sampling timing error caused by the frequency and phase offset of the local sampling clock. The HD-FEC(Hard Decision Forward Error Correction) code with 7% overhead is used as the threshold, the sensitivity of the system is better than –51?dBm.