The invention discloses a belt transmission-based vehicle-mounted pavement crack detection system verifying device, and aims to solve a verifying problem of a variable-width crack detection result ofa vehicle-mounted pavement crack detection system. The belt transmission-based vehicle-mounted pavement crack detection system verifying device mainly comprises a base (1), bearing bases (2), a driving wheel (3), a mother board (4), a transmission belt (5), a driven wheel (6), a subboard (7), a motor cover (8), spur gears (9), bearings (10), a motor (11) and a motor seat (12). The belt transmission-based vehicle-mounted pavement crack detection system verifying device which is small in occupied space, simple in structure, high in verifying accuracy, easy and convenient to operate, easy to mount, relatively low in cost and reliable in performance is provided.