The non-fully developed full-range sea spectrum (NDFSS) is reconstructed, and a fractal sea model based on NDFSS (NDFFM) is presented, witch is well applicable to the real sea surface. The two-scale method is used to calculate the backward radar cross section (BRCS) of the NDFFM sea surface, and the relationship between the model parameters and the BRCS is discussed in detail. Compared with the conventional fractal model and the real radar data, this model is proved to be accurate and efficient.