Abstract: Electromagnetic scattering computation for sea surfaces is fundamental to revealing sea surface scattering mechanisms and retrieving oceanic parameters. In recent years, microwave remote sensing at small incidence angles and in high frequency microwave bands has attracted increasing attention because of its unique measurement advantages. However, relevant scattering models remain insufficiently assessed, especially under moderate-to-high sea states and in high frequency microwave bands. To address this issue, this study analyzes the effects of wave spectra, environmental factors, and radar parameters on the simulation accuracy of the composite surface Bragg scattering model, the two-scale model, and the small slope approximation (SSA) at small incidence angles. The results show that SSA generally achieves higher simulation accuracy than the other models. An improved SSA-based model is therefore proposed by incorporating foam effects and Bessel functions to enhance simulation accuracy under moderate-to-high sea states and improve computational efficiency in high frequency microwave bands. Compared with classical SSA, the improved model reduces the root mean square error from 1.35 dB to 0.80 dB in the Ku band and from 1.43 dB to 1.21 dB in the Ka band. It also reduces the computational cost by more than 80% in the C, X, Ku, and Ka bands, with a maximum reduction of 98.53% in the Ka band.