The invention provides a method and a device for identifying access control identity based on ultrasonic waves. The method comprises the following steps of enabling each user to install an access control APP (application) at a hand-held mobile terminal, and use the ID (identity) to register as the user of the access control APP; generating an encrypting key and a decrypting key; enabling an access control machine to obtain the information of the users, and storing into a local database; when the distance between the hand-held mobile terminal and the access control machine is controlled within the setting range, using an encrypting algorithm and the encrypting key to encrypt the ID to obtain encrypting information, converting the encrypting information into a data frame, converting the data frame into an ultrasonic signal by an ultrasonic digital encoding type, transiting the ultrasonic signal via a loudspeaker, enabling the access control machine to receive the ultrasonic signal and convert the ultrasonic signal into the data frame, demodulating, and decrypting to obtain a plain text; if the plain text is matched with the information of the local database, automatically opening a door. The method and the device for identifying the access control identify based on the ultrasonic waves have the beneficial effects that the safety is higher, the use cost is reduced, and the reliability is higher.