Abstract: Accurate course control of a ship requires Quantitative prediction of the transvers-longitudinal displacement of the ship in maneuvering.This paper derives the formular for calculating the transvers-longitudinal displacement of a ship carrying way with engine stopped or accelerating under the condition of uniform flow field.Analysis shows that the track of a maneuvering ship is decided by the motion parameters of the ship and the flow filed.When a ship is approaching its destination, the navigator can set the course according to its initial speed and the current angle, then, stop the engine and let the ship sail to the destination along desired course.For a ship navigating to a planned narrow channel, similar way is feasible except the engine is running rather than stopped.