The internal reflection of nanosized gold cluster films was studied using the technique of polarization modulation of electromagnetic radiation in the Kretschmann geometry. We measured the reflection coefficients R s and R p of sand p-polarized radiation, respectively, as well as their polarization difference ∆R = R s − R p , as function of the light incidence angle in the 0.4÷1.6 µm wavelength range. A topological size effect was found; it consists in dependence of the value and sign of curvature of the polarization difference characteristics on the film surface properties. It is shown that the sign of curvature of ∆R characteristics depends on the radiation wavelength λ and indicates resonance interaction with a metal film of either p-polarized radiation only or that of both polarizations. The spectral characteristic of the topological size effect in the resonance interaction is obtained from the condition of isotropic reflection, ∆R = R s − R p = 0, and its dependence on the radiation wavelength.