A raised panel method based on NURBS (Non-Uniform Rational B-Splines) for free-surface flows with forward speed is presented. In this generalized panel method, NURBS are employed to represent the body geometry, disturbed free surface, and to express the unknown source strength distribution, on the body surface and above the free surface. Compared with common higher-order panel methods, it has no need of adopting local coordinates. NURBS make the geometry representation of the body shape and the wave patt more precise. Raised panels above the free surface produce less numerical dispersion error, need less CPU consumption and are helpful and combined with collocation-point shifting up-stream, can satisfy the radiation condition numerically. By using continuous and discrete Fourier analysis, numerical errors of this method are discussed and a general expression for the errors of numerical damping and dispersion, including the effects of the vertical distance of singularities to the free surface, the order of singularity distribution represented by B-splines in panels, and collocation-point shifting is derived.