Aiming at the difficulty of searching for physical evidence in complex environments by ordinary unmanned airborne cameras, a method using polarization imaging technology was proposed to conduct physical evidence detection and search. In order to ensure search efficiency and work under low illumination conditions, a large field-of-view and large relative aperture two-speed zoom polarization imaging optical system was designed. The system had a focal length of 11 mm and 22 mm, the F-number of 1.8 and 2.7, an angle of view of 60° and 34°, and a reasonable focusing method was given, which can achieve clear imaging at 3 m and 10 m flying height. After simulation analysis, the design results show that the modulation transfers function(MTF) of short focus and long focus is better than 0.45 at 91 lp/mm, and the imaging quality is better. Tolerance analysis shows that tolerances are well designed to meet imaging quality. The system is integrated with the micro-polarizer array detector and equipped with a drone platform, which can perform real-time and efficient physical evidence search on the crime scene in a complex environment, and greatly enhance the ability of cases to crack.