Abstract: In the preliminary design of a ship, in order to obtain a hull form with excellent resistance performance rapidly and accurately, the optimized design program of ship lines using optimal fullscale ship was developed, which combined the Rankine source method (one of the wavemaking resistance theory of potential flow ) and viscous theory with the optimization technique. In the optimization process, the SUMT interior point method of Nonlinear Programming (NLP) was proposed with reducing wavemaking resistance as the main objective function, with appropriate displacement as a basic constraint condition and the parameters of hull form modification function as design variables. Finally, the numerical optimization examples for different regions of forebody of fullscale surface vessel were provided, which indicated that the resistance was reduced distinctly by this optimal method.