Abstract: In order to achieve the ship still-water navigation speed,some prototype tests have to be implemented in flowing waters due to certain restrictions.The ship navigation speed in flowing waters is different from that in still water because the propulsive force can’t be completely transformed to be the driving force owing to the water gradient.Based on a series of vessel prototype tests for still-water navigation speed conducted in a flowing reach of the Lancang River,this paper presents two methods for correcting still-water navigation speed,the drag balance method and the resistance comparison method.Both methods lead to close results,and the drag balance method is simpler.Theoretical analyses and case studies indicate that whether navigation speed in flowing waters is able to replace still-water navigation speed may depend on the ratio of the resistance due to hydraulic gradient to ship’s propulsion.