An operating method of a vehicle watchdog circuit is provided. The method includes monitoring whether communication with a vehicle controller through a preset protocol is enabled and when a communication fault does not occur by monitoring whether communication is enabled, transmitting an error detection query to the vehicle controller every preset period. A response to the error detection query is received, and an operation of the vehicle controller is monitored, and upon determining that the operation of the vehicle controller is normal, a plurality of preset reset signals are sequentially transmitted to the vehicle controller.