A decoding method for MP3 bit streams, which replaces a buffer required in the decoding process by manipulating the order of data decoding. The decoding method includes reading the head and side information of the current frame, and calculating a main data's start address of the current frame. While decoding the main data, the head and side information of subsequent frames are skipped if the reading of the main data is not yet completed. The start address of the next frame is calculated and directly accessed after finished reading the main data of the current frame. An optimum method for accessing frequency lines utilizes the characteristics of the MP3 frequency line, instead of inserting a plurality of zeros in the rzero zone containing successive zeros, the initial boundary address of the rzero zone is memorized.