Remote sensing applications require developing accurate models to predict radar bistatic scattering from random rough surfaces. In this context, an improved two-scale model (TSM) is developed. The simplest TSM (TSM1) combines the first order small perturbation method (SPM1) with geometrical optics (GO) to be able to cope with both the small- and large-scale components of the surface. To get improved results at grazing angles and better depolarization estimation, we include the effects of multiscattering due to the target surface by adding the second order SPM (SPM2) contribution to SPM1 at small scale and develop an improved TSM (TSM2). The applications of TSM2 are presented for sea surface by assuming the surface-height spectrum of Elfouhaily et al., at grazing angles. In the backscattering configuration the numerical results are compared with the published experimental data and other approximate analytical models. Finally, we use the TSM2 to predict the sea scattering in the bistatic configuration and compare the results with TSM1.