The invention discloses an expanded circuit connected with a protection cabin controller of an ATM (Automatic Teller Machine) and a realization method of the expanded circuit. The circuit is characterized by comprising a logic module which is accessed after a child crying detection and recognition module is connected with a mono-stable circuit module in series; an output of a human body sensor is connected with an input of the logic module; the output of the logic module is accessed into an input end, which is connected with the human body sensor, of an original protection cabin controller; the logic module is characterized in that: when the mono-stable circuit module is at a stable state, the output of the logic module is the same as an output signal of the human body sensor; when the mono-stable circuit module is at a transient stable state, the output of the logic module is a logic electric level which is output when the human body sensor does not monitor a human body. The method is characterized in that a child crying simulated human body faint and falling signal and logic of the human body sensor are combined and then are transmitted to the input end, which is connected with the human body sensor, of the original protection cabin controller; the child crying simulated faint and falling signal is used for unlocking a cabin door and an original function for detecting and recognizing through the human body sensor of the protection cabin controller is kept.