QoS routing (Quality of Service) protocol is a routing mechanism which selects its path based on available network resouces and QosS requirements of business flow. It is also a dynamic routing mechanism which includes various Qos parameter. With underwater exploration activity continued to strengthen in recent years, the study of underwater wireless sensors sparked a research boom. In this paper, by setting the application of large-scale hydrological monitoring as its background, it analyzes the current QoS routing protocol of underwater wireless sensor networks. Moreover, it elaborats on the network topology structure, data forwarding mechanism and some other problems in the QoS protocol, and try to propose a way to improve the QoS routing protocol.