An apparatus, a system and a method for space status detection based on acoustic signal are provided. The detecting apparatus includes an audio transmitting device, an audio receiving device, a signal processing device and a decision device. The audio transmitting device transmits an acoustic signal into a space. The audio receiving device receives a varied acoustic signal as a sensing signal. The signal processing device is coupled to the audio receiving device to receive the sensing signal and generates a characteristic parameter of a space status according to the sensing signal. The decision device is coupled to the signal processing device to receive the characteristic parameter and detects a change of the space status according to the characteristic parameter.