In this paper

a model is proposed to estimate the brightness temperature of vegetated surface based on ray tracing technique to account for increasing multiple scattering effects as frequencies goes higher. The vegetation layer is composed of discrete scatters such as leaf

branch and stalk. The multiple scattering inside the vegetation layer and that between the vegetation and soil surface is accounted for by Matrix Doubling. The surface emission is calculated by IEM（Integral Equation Method） algorithm. Simulation results at higher frequency show that the emission from vegetation layer is dominant

and that the vegetation has obvious extinction to surface. A good agreement is obtained by comparison of the simulation with air-bone PSR（Polarimetric Scanning Radiometer） C\|band data

and X- and Ku-band data from AMSR-E.