The invention relates to an MACA-U (Multiple Access Collision Avoidance for Underwater Wireless) protocol-based underwater acoustic network multiple-address accessing method. The method comprises the following steps in an RTS-CTS exchange process of a source node and a destination node, if the source node or the destination node receives an RTS transmitted by the other node, on the premise that the existing time of the source node or the destination node is enabled to not conflict, calculating the time when the source node or the destination node is suitable for the receiving of a data frame transmitted by the other node; replying a CTS to the other node, wherein the CTS comprises the time waited by the other node from the time when the CTS is received to the time when the data frame is transmitted, and the silence time after the time when the other nodes except the other node receive the CTS; after the other nodes receive the CTS, transmitting the data frame after waiting for some time according to the CTS.