In this paper, panel method and CFD software FLUENT have been used for the calculation of the interaction of propeller and rudder with additional thrust fin. Through changing dimensions, this paper investigates the principal parameters that affect additional thrust efficiency of additional thrust fin, so as to provide the theoretical basis for the design of the thrust fin. This paper mainly consists of four parts, as follows:Panel method was used to calculate the lifting coefficient and drag coefficient of short foil. The geometry of three dimension vortex sheet of the sides of foil and its trailing were determined by the kinematic boundary condition. A new calculation model of three dimensional short foil was used to simulate the phenomenon of tip vortex and its roll up. The computed results agree fairly well with the experimental data, which indicates that the flow solver of this paper is useful in simulating the performance of three dimensional short foil.Panel method was used to calculate the steady and unsteady performance of propeller. The influence of ship hull was given as unsteady flow on the face of the propeller. The comparison between the experimentation and calculation data of distribution of pressure proved the correctness of the program of this article.Panel method was used for the calculation of propeller and rudder with additional thrust fin. Hydrodynamic interaction between them was achieved by interactive calculation. Thrust and torque of one blade were calculated as the propeller rotating. Several kinds of wake models were applied to calculate the performance of additional thrust fin. The schilling section fin was firstly used as additional thrust fin. Through changing dimensions, this paper investigates the principal parameters that affect additional thrust efficiency of the thrust fin.The CFD software FLUENT was used to simulate the thrust and torque coefficient as the function advance ratio of some propeller and the thrust efficiency of additional thrust fins. The pressure and velocity of propeller and the flow behind the propeller were calculated. The thrust efficiency of fins were calculated while the change of the number of additional fins and the change of the angle attack..