With the development of marine economy, underwater wireless sensor networks(UWSNs) has been increasingly becoming mainstream. An uneven clustering algorithm based on gradation is proposed to solve the problem of difficult centralized clustering, uneven energy consumption and high-delay with underwater acoustic. Firstly, the cluster head node is sclected by using the threshold function combined with the node average energy and the node density, and the cluster head competition radius function considering the node depth and density, so that the distribution of the cluster head node is more reasonable and even. Then the cluster head grade is divided to balance the load of clusters with different inter-cluster transmission tasks. Finally, aiming to reduce the overall communication energy consumption and delay, inter-cluster multi-hop transmission routing is built combined with the cluster head level and greedy algorithm. Simulation results show that the proposed algorithm can not only balance energy consumption and prolong the network lifetime, but also effectively reduce the network communication delay.