Firstthe characteristics of laser phase noise under different laser linewidth conditions are analyzed.Thena theoretical model of the influence of laser phase noise on detection performance of coherent lidar is established.Finallythe influence of laser phase noise on performance of coherent lidar is analyzed by statistical simulation specific to two typical cases including pulse coherent lidar and FMCW coherent lidar.The research results show that:1) In the case of pulsed laserthe influence of laser phase noise on detection performance has little relationship with detection rangeso it is unnecessary to restrict the detection range to be less than the coherent length;and 2) In the case of FMCW coherent lidarthe detection performance is much susceptible to laser phase noiseso it is necessary to restrict the detection range to be less than the coherent length with one order of magnitude.