The invention provides an underwater acoustic network reservation multi-access method based on active time reversal, and relates to the technical field of underwater acoustic communication and underwater networks. Multiple access in the data transmission process among nodes, which is applicable to a distributed acoustic network MAC layer, is adopted, so that the transmission conflicts are avoided, the success probability and channel utilization rate of once transmission are substantially improved, and the networking energy consumption is lowered; by means of active TR space-time focusing and the space change characteristic of an underwater acoustic channel, the disadvantages are converted into advantages, the broadcasting characteristics of the underwater acoustic channel is weakened, the signal interference among adjacent links under a distributed multi-hop environment is effectively isolated, and the good transmission concealment and security of the multi-access method are realized by channel broadcasting weakening, so that the space multiplexing is improved, the network throughput is increased, the time delay of the system is shortened, and energy is saved.