Interface conversion device and on-board diagnosis system

The embodiment of the invention discloses an interface conversion device and an on-board diagnosis system. The interface conversion device is applied to the on-board diagnosis system which comprises a code reading card diagnosis apparatus, an automobile ECU and an automobile OBD interface, wherein the interface conversion device is used for being connected with the automobile ECU through the automobile OBD interface; monitoring a data reading request from the code reading card diagnosis apparatus, and conducting converting processing on the automobile OBD interface according to the data reading request and sending the data reading request to the automobile ECU through the automobile OBD interface; when the interface conversion device receives feedback data acquired by the automobile ECU according to the data reading request, the interface conversion device transmits the feedback data to the code reading card diagnosis apparatus. The embodiment of the invention further discloses the on-board diagnosis system accordingly. By means of the interface conversion device and the on-board diagnosis system, the compatibility of interfaces between the code reading card diagnosis apparatus and an automobile is improved through conducting converting processing on the automobile OBD interface.