Abstract: Numerical study of the open water performance of B series propellers is conducted in this paper,with the regression equation,which comes from the open water test of B series propellers,programmed using VB language,and the viscous flow field analyzed based on RANS method. The process involves FORTRAN program,Pro/E and GAMBIT to establish the propeller model. Then,the open water performances of B4-40 propellers are compared under different kinds of turbulence models;the numerical results and the parameter matching problem of tandem propellers are studied,and the changes of wakes and axial velocity distribution are observed. The results show that the RSM model is superior to other turbulence models,and the reasonable angle and distance between the blades of tandem propellers significantly improve the propulsion efficiency. The tandem propellers can effectively absorb the energy of trailing vortex,and as the distance of the disk increases,the axial velocity of the tandem propellers decreases faster than that for a single paddle,so the open water efficiency of the tandem propellers can be greatly increased.