The invention discloses a swing fan mechanism based vehicular pavement crack detection system testing device and aims to solve the problem of testing variable-width crack detection results of a vehicular pavement crack detection system. The swing fan mechanism based vehicular pavement crack detection system testing device mainly comprises a flexible shaft supporting seat (1), a fixing shaft (2), afixed fan (3), an expansion bushing (4), a swing fan (5), a counterweight line (6) and a counterweight (7). The swing fan mechanism based vehicular pavement crack detection system testing device hasadvantages of small space occupancy, simple structure, high testing precision, simplicity and convenience in operation, easiness in mounting, low cost and reliability in performance.