Aiming at the difficulty of node replacement and limited energy of underwater wireless sensor network, the paper proposes an energy-efficient routing protocol based on improved sine cosine algorithm. In the process of cluster formation, it uses the improved sine cosine optimization algorithm to select the cluster head, considering the three factors of energy, node density and communication distance, and discusses the corresponding weights, then designs a more reasonable fitness function for cluster head selection. Singlehop transmission within the cluster, between the clusters used multihop transmission. The algorithm transmits the collected information to water surface by limiting the depth, energy and forwarding area to select the appropriate next hop. The network simulation results show that under same conditions, the work hours increases by 6910%,2478% and 1494% compared with the traditional LEACH algorithm, the KACO and DUCISCA algorithm, which can effectively balance network energy consumption, prolong network life, and improve data transmission rate.