The invention discloses a flexible cover plate based shading device of a vehicle-mounted pavement crack detection system, and aims to solve the problem of flexible light shading of a vehicle-mounted pavement detection system. The flexible cover plate based shading device consists of a base 1, a bearing seat 2, a right fixing rack 3, a left fixing rack 4, a driven wheel 5, a driving wheel 6, a transmission belt 7, a folding cover plate 8, a tension spring 9, a camera 10, a motor 11, a camera base 12, a driven wheel shaft 13 and a left fixing rack clamp 14. The invention provides the flexible cover plate based shading device which is simple in structure, simple and convenient to operate, easy to mount, relatively low in cost and reliable in performance, of the vehicle-mounted pavement crack detection system.