Abstract: The present disclosure discloses a device, a system and a method for recognizing the action of a detected subject. The device includes an input section for the user to input scene mode selected among a plurality of scene modes; a detection section for detecting the action of the detected subject and outputting an action signal when the device is disposed on the subject; and a microprocessor for processing the action signal according to the selected scene mode, to recognize and output the action of the detected subject in different scene modes. The system includes a device and a terminal, wherein the device is used to recognize the action of the detected subject based on a scene mode selected through the terminal by a user; and the terminal is used to display the action recognition result. The method includes recognizing the action based on a scene mode selected by a user.