The invention discloses a watchdog circuit for an automobile electronic controller. The watchdog circuit for the automobile electronic controller comprises a power supply module which is used for supplying power to a power amplifying module, a voltage monitoring module and a signal output module; the power amplifying module is used for receiving a PWM (Pulse-Width Modulation) signal which is output by a single chip microcomputer, amplifying the power of the PWM signal, and outputting the power-amplified PWM signal to a square wave detecting module; the square wave detecting module is used for detecting the PWM signal; the voltage monitoring module is used for detecting a voltage signal which is output by the power supply module; the signal output module is used for receiving level signals which are output by the square wave detecting module and the voltage monitoring module, and outputting different alarm signals, resetting signals and limping mode enable signals to the single chip microcomputer according to the different level signals. According to the watchdog circuit for the automobile electronic controller, the hardware watchdog circuit is formed by adopting discrete devices; the alarm signals and the resetting signals can be generated and a limping mode can be started when a program of a microprocessor is abnormal, and the functional safety requirement of the automobile electronic controller is met.