The invention discloses vehicle-mounted fault diagnosis system and method for a hybrid electric vehicle based on CANopen, belonging to the field of vehicle fault diagnosis. The vehicle-mounted fault diagnosis system for the hybrid electric vehicle based on CANopen comprises a fault diagnosis interface, an information acquisition module, a storage module, a liquid crystal display module, an audio alarm module, a touch screen and keyboard module, a main control module and a power source module. When a fault occurs, the diagnosis system as a CANopen master station utilizes an emergency message to trigger a SDO (Service Data Object) to read the fault diagnosis information of an object dictionary item corresponding to the fault, analyzes the fault information and stores the fault information in a fault information management unit; meanwhile, the fault information is displayed in a fault diagnosis interface. The invention completes the real-time acquisition and display of the fault information and vehicle real-time data and the effective management of the fault information.