A traffic information extraction and calculation-based method for processing data of license plates comprises four steps: step (1), a vehicle license plate recognition database is established in a computer at a background processing center; step (2), vehicle license plate data, the starting point and the destination of which are designated by a user is initially matched, and a vehicle travel time testing database is established in the computer at the background processing center; step (3), information granules of a route designated by the user is structured, and ambiguous route noises in the vehicle travel time testing database are eliminated according to computer operating procedures, and then a vehicle travel time database of the designated route is acquired; and step (4), by the computer operating procedures, information granules of travel time are structured, and vehicle travel time noises in the vehicle travel time database are eliminated, and then precise travel time is acquired. The method can improve the accuracy of the vehicle travel time data, has important practical value in the field of intelligent transportation, and can be widely applied to situations such as traffic management, monitoring, law enforcement, electronic toll collection, and traveler information service.