Aiming at the problem that the omnidirectional sea-wave spectrum of fractal sea-wave model cannot satisfy the positive power law when the spatial wave number is smaller than the fundamental wave number, one-dimensional (1D) sea-wave model is proposed by combining statistical sea model and normalized band-limited Weierstrass-Mandelbrot (WM) fractal sea model. With the proposed method, the closed form expression of the omnidirectional sea-wave spectrum is calculated, and the obtained omnidirectional sea-wave spectrum is in good agreement with the commonly used Pierson-Moscowitz (PM) spectrum. The electromagnetic scattering coefficient of the improved model based on two-scale method is derived. The angular distributions of the scattering coefficient of Longuet-Higgins model, classical fractal model and improved model are analyzed. Simulation shows that the difference among the three model′s scattering coefficients is caused by the large scale of sea-wave, which proves the validity of the model. The results are also validated by real data.