The invention discloses a portable automatic alarm power-off protection device. The device comprises a control module, a detection module, an alarm module and an AC (alternating current) control module. An output end of the detection module is connected with an input interface of the control module. An output end of the control module is connected with an input end of the alarm module, alternatingcurrent voltage is connected with a power input interface of the control module through an AC/DC voltage transformation module, a control output end of the AC control module is connected with an AC output interface, and a control input end of the AC control module is connected with the alarm module through a contact of the alarm module. Whether a person enters a preset monitoring area or not is detected through the detection module, the control module is triggered to output a control signal, the high-voltage output of a main loop is controlled through the AC control module, meanwhile, a soundalarm is given out, the protection circuit has simple logic, the setting is convenient and easy to realize, and the practicability is high.