Abstract.A model is considered that explains mechanism of non-thermal action of microwave radiation on the thin SiO 2 (ТiO 2 , Er 2 O 3 , Gd 2 O 3 ) film/SiC and SiO 2 /GaAs structures. It assumes that the centers of electron-hole recombination are redistributed because of resonance interaction between dislocations of certain length and microwave radiation. As a result, additional bands appear in photoluminescence (PL) spectra of the oxide film/SiC structures or intensities of some bands are redistributed in the PL spectra of the SiO 2 /GaAs structure, as well as optical density of the oxide film/SiC structures changes.