It is well known that a single anchored ship causes often the slewing motion by disturbances such as current, wind and wave. This slewing motion will be undesirable factor on anchoring ship, and it will be of importance to restraint this slewing motion for safety of navigation, operation and traffic control at the restricted sea. In this paper, two types of control system are proposed for restraint the slewing motion of a single anchored ship, and the characteristics of each type of control system are discussed by simulation of the slewing motion. One of these types is named “WIDE CONTROL”. This aims that the ship is always in equilibrium condition under external disturbances such as current, wind and wave. The other type is “NARROW CONTROL” which aims that the heading direction of ship coincides with the direction of current. The former control will be useful for anchorage being unrestricted sea, the latter control for restricted sea. From the results of simulation on restraint of slewing motion, it is shown that the slewing motion of a single anchored ship will be restrained by using the two types of control system proposed in this paper properly corresponding to the external disturbances.