The invention discloses a shading device based on a hydraulic turnover mechanism and used for a vehicle-mounted road crack detection system and aims to solve the problem about hydraulic turnover mechanism based shading of the vehicle-mounted road crack detection system. The shading device based on the hydraulic turnover mechanism and used for the vehicle-mounted road crack detection system mainlycomprises a base (1), shaft bases (2), a shaft (3), a shading plate (4), a hydraulic rod extended piece (5), a hydraulic cylinder fixing piece (6), a spring (7), a hydraulic cylinder (8), a check ring(9) and a safety pin (10), wherein a tube in the middle of a round steel plate of the hydraulic rod extended piece (5) is mounted on a hydraulic rod of the hydraulic cylinder (8) in a sleeving manner, a bolt penetrates a round hole in the tube in the middle of the round steel plate of the hydraulic rod extended piece (5) to be in threaded fixed connection with a threaded hole in the hydraulic rodend part of the hydraulic cylinder (8). The shading device based on the hydraulic turnover mechanism and used for the vehicle-mounted road crack detection system is simple in structure and reliable in performance.