In this paper, the authors presents some results of a study on used a commercial Computation of Fluid Dynamic (CFD) to analysis hydrodynamic performances of a ship and the effects of computated conditions on the CFD results of viscous resistance acting on hull of a ship. In the CFD computation, we must do step by step as well as: design model, design computed fluid domain and meshing, setup boundary condition and run. Each step has a certain effect on the computed process and the CFD results. In this paper, the authors present some results of research on effects of computed fluid domain and meshing on the CFD results. This research is important for the problems of the simulated ship hydrodynamic by used CFD as well as the general CFD problem.