Abstract: This paper gives a 3D-entity model of themain part of the underwater vehicle by use of Pro/E software. Based on the3D Navier-Stokes equations for viscous steady imcompressible flow andtwo-equation \kappa-\varepsilon turbulent model, the flow field andhydrodynamic load of underwater vehicle during empennage-expanding isnumerically simulated with the finite volume method. The empennage-expanding is analyzed by the use of the simulation results. Comparing with theexperimental results, the numerical analysis method is justified, whichmay be useful for analyzing engineering problems.