Mathematical model of maneuvering motion for a single-screw single-rudder ship is established and several applications to the special situations of maneuvering are attempted. While, the mathematical model for twin-screw twin-rudder ship is not presented so much, because that type of ship is not popular. Lee et al. have examined the characteristics of such ship by captive model tests in 1988, in Japan. This paper proposes new mathematical models for propeller effective wake (1 -${omega}_p$) and effective neutral rudder angle ${delta}_R$ in the case of twin-screw twin-rudder ship. And some maneuvering motionse are calculated with proposed models and compared with exact simulations.