Aiming at the low signal-to-noise ratio (RSN) and difficult extraction of coherent lidar echo signal in the far field, we propose pulse coding technology to improve the RSN and dynamic range of the system, then we study the encoding and decoding principle of Golay code in coherent lidar system, and theoretically analyze RSN improvement of the system by using pulse coding technology. We simulate the echo signal of coherent Doppler lidar based on the atmospheric slices model, and obtain the wind velocity of the pulse coding system based on the decoding principle. The simulation results show that, when the Golay code pulse is used as the detection pulse of the coherent lidar, the wind velocity error is less than 3 m·s-1 in the range of 0~5.3 km with the distance resolution of 60 m and the time resolution of 1 s. In the same measurement time, the coherent lidar with pulse coding technique can improve the detection distance by 2.5 km compared with the traditional pulse coherent lidar, which improves the RSN of the far-field weak signal.