Three-dimensional imaging lidar is a new type of active detection technology, which can obtain target spatial information accurately and quickly. It has a wide application in the fields of target detection and recognition, scientific research detection, mapping and navigation, etc. Three-dimensional imaging lidar has many modulation modes, among which the non-scanning three-dimensional imaging lidar based on polarization modulation has the advantages of long measurement range, high measurement accuracy, fast imaging speed and no motion artifacts, which is one of the hot research directions in this field. In view of this technology, this paper analyzes the principle of polarization modulation imaging by Jones matrix calculation, and obtains the geometric relationship between the imaging illumination values in four polarization directions and the polarization modulation phase delay of Pockels Box. Then, a set of laser radar optical system based on polarization modulation imaging is designed by using optical software. The analysis results show that the designed optical system has good imaging quality, clear target edge imaging and can distinguish independent square targets with a diameter of 1m; The light outside the field of view of the strip light source does not enter the detector, so the system has less stray light and less imaging distortion; At last, the input phase delay δ of the Pockels box in the simulation model is randomly set to different values, and the illumination values of four polarization directions are obtained by imaging simulation, so that the phase delay δ′ of the Pockels box is inverted. The results show that | δ′-δ | ≤ 5.2× 10-6 λ, which proves that the polarization modulation method is correct.