Abstract: Doppler wind lidar with its high resolution, high precision, large detection range, the ability to provide three-dimensional wind field information, has attracted the attention of multinational scholars, and put a lot of manpower and material resources to carry out research. The Doppler wind lidar was designed to obtain single longitudinal mode, narrow linewidth and high power laser output by seed injection. The slow drift of the center frequency of the laser, ambient noise, laser rod temperature change or the vibration disturbance may cause the failure of seed injection. Then the laser spectrum was transformed from a single longitudinal mode output to a multiple longitudinal mode output. The linewidth of single longitudinal mode laser output was about 200 MHz. However, the multi-longitudinal mode laser output had a wide linewidth,which led to widened Rayleigh backscattering spectrum and then great speed errors in the speed inversion condition. The pulse screening circuit was developed to filter the multi longitudinal mode pulse during the data acquisition, which can effectively reduce the error of wind speed inversion and improve the precision of wind speed measurement.