The invention discloses a cross-layer design-based underwater wireless sensor network life cycle prolonging method. The method includes the following steps that: (1), an underwater wireless sensor network maximum life cycle model is built; and (2), an iterative algorithm is executed, the optimal scheme of a network transmission scheme which contains the data rate and transmission power of nodes, and network link scheduling is obtained. Compared with the prior art, the method of the present invention can realize the reduction of the energy consumption of the nodes and energy consumption balancebetween the nodes in the network, thereby effectively prolonging the life cycle of the network.