In order to eliminate the uncertainty caused by the inclination of a beam, a dual polarization laser Doppler velocimetry system is established. We use a structure with two beams and two probes to detect the motion of the object. Firstly, the angle between the two beams is obtained by a calibration experiment. For any beam inclination, the scattered beam on the surface of a moving object is collected by a dual-probe device, and the Doppler shift of the two interference signals is obtained by combining the dual polarization optical path structure. Then, the refined framing algorithm is applied to demodulate the two interference signals in real time. The real speed of the object is obtained through the synthesis of the two speed components. The experimental results show that the average deviation between the measured value and the theoretical value can reach 1%-5% when the speed is within the range of 10 mm/min~1500 mm/min. In the process of non-stationary motion, the mean RMSE of the v-t image corrected by the refining frame segmentation algorithm is 1.19 mm/min. The system’s structure meets the requirements of stability and reliability, high precision and strong anti-interference ability in speed measurement.