1. A gesture recognition apparatus for recognizing a gesture made by a person, comprising: an ultrasound transmitter configured to send ultrasound signals; a ultrasound receiver configured to receive reflected ultrasound signals from an object; a dividing module configured to divide the reflected ultrasound signals into a plurality of frames according to a time interval; a computing module configured to obtain an eigenvalue of each frame; a classifying module configured to filter the eigenvalues to obtain gesture eigenvalues, and to obtain a matrix of probabilities of the gesture eigenvalues by using a sound recognition model; a gesture library comprising a plurality of reference matrixes of probabilities corresponding to a plurality of reference gestures; and a recognition module configured to search a reference matrix of probabilities from the gesture library for a match to the matrix of probabilities of the gesture eigenvalues; and recognize the gesture eigenvalues as a reference gesture corresponding to the reference matrix of probabilities if the reference matrix of probabilities is found.