A constant power limiter includes a control circuit and a power source circuit thereof, and the control circuit includes a voltage detection circuit configured for detecting a voltage of power source; a current detection circuit configured for detecting a load current; a zero-cross detection circuit configured for detecting a zero-cross point of AC power; a load driving circuit including a controlled silicon; and a micro control unit (MCU) configured for receiving output signals from the voltage detection circuit, the current detection circuit, and the zero-cross detection circuit, and outputting a control signal respectively to the load driving circuit to control a load power, wherein when the load power is less than or equal to a set power value, the load driving circuit has the controlled silicon fully open, when load power is no less than the set power value, the load driving circuit has the controlled silicon conduction angle decreased to stabilize the load power at the set power value.