Abstract: The engine of ships is laid off at anchor. Ships drift with wave and loss the capacity of controlling navigating direction for self, so the roll is increased and severer than shipping state. It is important to study stabilizer when a ship is at zero speed. In this paper we study the llft model of fin stabilizer that based on potential theory of the Weis-Fogh mechanism when a ship is at zero speed. Firstly, we discussed that Weis-F ogh mechanism how to rotate to generate the lift that has been given. According to the theory of Riccati differential equation, conditions that assure the existence and stability of period solution are given. Then, usi ng Runge-Kutta methods, the numerical solution of the model is obtained. Finally we give the conditions that assure the numerical solution is stable. The results are closely matched with numerical experiments.