The utility model relates to an automatic on-off alarm watch, which is composed of a united alarm watch machine core, a watch case, a two-plug connector a three-plug connector, a micro switch and a wire. The micro switch arranged in the clock case is restricted by the alarm setting spring of the united alarm watch machine core, the alarm setting spring is bounced, and the micro switch is supported to switch on an electric source. After one hour later, the alarm setting spring is dropped, the micro switch is reset, with the electric source switched off. When the utility model is used, the electric source, the automatic on-off alarm watch and a household appliance (special suitable for an electric cooker) are connected by a special plug wire. The turn-on time of the electric source is determined on the alarm watch, with the button of the electric cooker pressed. The alarm watch function of the utility model is unchanged, and the utility model also has the function that the household appliance is caused to operate in predetermined time.