In order to enhance the efficiency and safety of a ship sailing in rough seas, the authors aim to develop a ship dynamic performance system, which can be used to predict ship motion responses, wave loads as well as quasi-mean added resistance. Two-dimensional strip theory discretized by the source distribution method is implemented to calculate Response Amplitude Operators (RAOs) for 6 DOF motion as well as the wave loads for the vertical shear force and bending moment. In addition, the ITTC directional wave spectrum of the short-crested wave adopts the one-hundred years return sea state as the input for testing the sea-keeping performance. Subsequently, we developed a database for a specific ship to realize the relationship between the sea-keeping performance and a combination of wave headings and ship speeds. Since the calculation of hydrodynamic coefficients correspond to the instantaneous hull form below the free surface (draft), the Bspline curve fitting technique based on the fourth order Runge-Kutta method is introduced to describe the relative wave heights together with second order nonlinear forces.