In gravitational-wave detection systems, the surface scattering properties of ultra-smooth optical components play a crucial role in achieving high-precision gravitational-wave measurements. To analyze and predict the surface scattering properties of ultra-smooth optical components accurately and rapidly, a non-paraxial scalar scattering model, the Generalized Beckmann-Kirchhoff (GBK) model, was built up. On this basis, the influences of both the incident angle and the scattering azimuth angle on the angular resolved scattering distributions of both P-polarized and S-polarized incident light were investigated. Under different statistical distribution characteristics of optical surfaces, the effects of incident angle, azimuth angle, autocorrelation length, slope, cut-off frequency, and surface roughness on the scattering angle resolution distribution were analyzed. The research results can provide useful references for the manufacturing of ultra-smooth optical components and the generation and mitigation of stray light in gravitational-wave detection systems.