In recent years,frequency modulated continuous wave (FMCW) lidar has become an attractive option of sensors in the field of autonomous driving. This paper first introduces the ranging principle of FMCW lidar based on IQ modulator,performs parameter calculations for the design specifications,and then investigates the effects of under adverse weather conditions on the system performance using the constructed model. The results show that the model can accept a certain range of adverse weather variations,which provides the reference for the subsequent design and hardware selection of vehicle FMCW lidar system.