Power plug's current transformer and the live wire in the plug body are connected, and current transformer and voltage follower circuit are connected, and voltage follower circuit is connected with comparator and charging and discharging module respectively, and comparator, pilot lamp, buzzer, display screen, button, electric energy metering circuit and wireless module are connected with the singlechip respectively, and charging and discharging module supplies power for each components and parts respectively to for battery measurement provide the basis, be fixed with the pull ring on plug body. The utility model discloses can warn the user and pull out the plug when electrical apparatus converts the standby into, charging and discharging module has two kinds of power supply modes, does not need plus the power, saves the electric energy, voltage follower circuit makes the voltage of current transformer output send comparator and charging and discharging module respectively to, has simplified circuit structure, has reduced the design cost, the design has the pilot lamp on the pull ring of plug body rear surface, and the user that lets that can be very striking sees the pilot lamp state, has still made things convenient for pulling out of plug to insert.