The present invention provides a computer-aided conversion system and method for generating intelligible speech that uses a transmitter disposed in the nasal cavity of a user and a receiver disposed in pairs with the transmitter, the transmitter transmits a detecting signal in waveform to the nasal cavity of the user, and the receiver receives a reflected wave from the user's nasal cavity. After analyzing the reflected wave, a spectrum corresponding to the acoustic model of an articulatory cavity is obtained. Through the spectrum, the intention in the speaking of the user may be known, that is, the present invention may detect a speech not originated from the vocal cord of the user.