Abstract: In order to improve the capability of wind lidar, based on mathematics modeling method and circulator principle, the transmitted beam quality of circulator was analyzed. The influence of divergence angle on the peak intensity at target distance was discussed. The definition of coupling efficiency of circulator was proposed. And the influence of misalignment between transmitting and receiving axis on detection range was researched. Experimental platform was built to obtain spot parameters in the far field. The simulation results were verified. The results show that, the relative peak intensity at the same distance decreases with the increasing of divergence angle of transmitted beam. The detection range of lidar is mainly affected by misalignment, and misalignment of mrad would make detection range decrease by 89.7%. Therefore, the collimation ratio of optical antenna should be increased reasonably and the structure precision for adjusting misalignment should be better than 0.1mrad level.