Abstract: A system for diagnosing a grade of a used car according to an embodiment of the present invention includes: collecting basic information of a used car by using a module, and transmitting the same to a server; transmitting grade information of the used car to the server; securing big data within a database; securing an inference engine within the server by using enhanced learning information obtained by performing enhanced learning of relation between the basic information and a grade of the used car by using artificial intelligence; and collecting basic information of a used car to be diagnosed and transmitting the same to the server, and diagnosing a grade of the used car to be diagnosed based on the basic information of the used car to be diagnosed by using the inference engine.