The invention relates to an automobile combined meter having an automobile electric control diagnosis function and a diagnosis method thereof. The automobile combined meter comprises a central controller, a meter interface, a plurality of multifunctional indication step motors electrically connected with the central controller respectively, a meter illumination indicator lamp, a safety status indicator lamp, multifunctional indicator lamps, multi-fault indicator lamps, a display screen, a clock chip, a storage, a voice prompt module, a key processing circuit, a power module electrically connected with the meter interface, a plurality of input signal processing circuits electrically connected with the central control unit and the meter interface respectively and an automobile electric control diagnosis interface circuit, wherein a controller area network (CAN) bus interface and a universal asynchronous receiver/transmitter (UART) interface are arranged on the central control unit. When the automobile combined meter used, the meter interface is electrically connected with the electric control unit of the automobile to be diagnosed, and the central controller is connected with the automobile electric control diagnosis interface circuit through the CAN bus interface or the UART interface and then communicates with the the electric control unit of the automobile to be diagnosed through the meter interface. Having the automobile electric control diagnosis function, the automobile combined meter can prompt the fault of the automobile and make the fault point clear so as to prompt drivers to maintain the automobile better.