The invention provides an identification system and a method of unlicensed motor vehicles. In the prior art, the unlicensed motor vehicles are artificially identified by the traffic police, therefore, the efficiency is low. The method comprises the following steps: firstly, storing the theoretically shortest travel time between any two monitoring intersections at the processing center end; secondly, monitoring and taking the images of the motor vehicles passing by at the monitoring intersections, recording the moment at which the images are taken and transferring the taken images, the moment and the monitoring intersections from a network system to a processing center; thirdly, receiving the images, the moment and the monitoring intersections at the processing center end, identifying the license plates from the images and storing the license plates, the moment and the monitoring intersections into a database to be detected; fourthly, computing the actual travel time of the motor vehicles with the same license plate between any two monitoring intersections, judging whether the actual travel time is less than the theoretically shortest travel time between any two monitoring intersections, if yes, determining the motor vehicles to be the suspected unlicensed ones. The invention can improve the identification efficiency of the unlicensed motor vehicles.