Aimed at 3D Rankine panel method, a method for panel generation of ship hull and free surface based on Bspline was proposed in this paper. The bicubic B-splines was used to represent the geometric form of the ship hull and the generalized cross sections was used to describe more accurately the shape of bow and stern. The compatibility problem of the splines was solved by reconstructing the section curves twice. Parameterized discretization was conducted for the hull and different free surfaces. By modifying the parameter partition, the panel mesh density can be easily changed to meet the requirement of numerical computation.