Abstract: A new physical model for forward scattering of a polarized light beam in atmosphere transmission was established. Based on incoherent light assumption, double and multiple forward scattering theories were derived. To the symmetrical system, the effective Mueller matrix of the forward scattering of polarized light was obtained. It is shown that only seven matrix elements are independent, nine matrix elements are obtained by rotating independent elements. To validate the scattering model, the effective Mueller matrix of the forward scattering of polarized light in 10km atmosphere transmission were simulated with Monte Carlo method, it is proved that theatrical and numerical results are in good agreement.