Abstract: An authority limit management method is proposed for a digital media storage. The digital media storage includes at least one micro processor and at least one memory unit and connected to an access device. A classification authorization code index (CAC index) and a plurality of classification operation commands (COC) is pre-stored in the digital media storage and an identification code is set for the access device. The classification operation commands is performed to calculate a classification authorization code when the digital media storage is connected to the access device for initial transmission protocol. The authority limit of the memory unit for the access device is granted to the access device according to the classification authorization code. Therefore, the data of the digital media storage can be prevented from illegal copy or hacker.