Abstract： Theory prediction method of ship/propulsion interaction is the technical difficulty for predictions of shipspeed performance. A viscous RANS/panel method coupling with the iterative method was proposed to simulate ship/propulsion interaction based on the viscous CFD/potential flow theory. The viscous flow around surface ships was computed by the CFD method and hydrodynamic loads for propellers were computed by the potential panel method. The total velocity in the domain of propeller plane was obtained by viscous solver. The inducedpropeller velocity was substracted from the total velocity, and the effective velocity was obtained and used as the propeller inflow. The effective wake velocity was renewed to calculate the force and induced velocity by the potential solver. Then the iteratations were recycled. The propeller effects were treated as body force terms. The present results of calculation were compared with the experimental data, which shows that the coupling method can solve the ship/propeller interaction very well, and the computational cost is significantly reduced. The coupling method proposed, which incarnates viscous effect and efficiency of potential flow computation,  can be extended to predict ship/propulsion interaction performance and used for design and optimization research.