In the present research, hydrodynamical and aerodynamical characteristics of a high-speed planning hull is studied using computational fluid dynamics. Simulations are three-dimensional with considering a two-phase turbulent flow. To obtain sinkage and trim of the hull, two degrees of freedom is assumed for it. Rigid body dynamic equations and governing equations of the fluid are coupled using 6DOF solver and dynamic mesh technique. Based on the available experimental results, simulations of the aimed high speed hull are performed in the linear velocity range of 0.9-8.31 m/s. Comparing the present numerical results with the experimental data, shows that maximum average error for resistance, trim and sinkage in different velocities does not exceed 10%. This shows the accuracy and proficiency of the current model. Mesh independency of solutions is studied for all velocities and the results are reported based on the most suitable mesh. At the end, the effect of applying steps on reducing the drag and improving stability of the hull is investigated for several states in one and two steps. Finally, the most optimized state is introduced and relating results are given. Results show that applying steps to the mentioned high speed hull reduce the overall resistance by 11%.