For the problem of carrier frequency drift in coherent optical communications, according to the actual coherent optical communication system, we adopt the binary phase shift keying (BPSK) and quadrature phase shift keying (QPSK) modulation modes respectively, and simulate the frequency shift to cause the rotation of the constellation map and the increase of the bit error rate. Based on laser frequency adjustment and control principle, adopting the method of external phase detector, single-chip computer(STM32) and piezo-electricity (PZT) driver amplifier at the signal output end, we design a circuit based on feedback decision control loop, which is used for tracking the frequency of the local oscillator laser to the frequency of the signal laser so as to stabilize the carrier frequency. The experimental results show that the feedback decision circuit can stabilize the frequency drift within the range of ±2 MHz when the intermediate frequency carrier is considered as the reference 100 MHz, which is beneficial to the processing of the demodulated signal, and the frequency drift compensation range can reach GHz magnitude. This scheme is simple and practical, which is suitable for coherent optical communication system.