Research has been done on the composition and properties of natural thin film surface porous silicon (PS) coating as well as polymetacrylic acid films precipitated from water solution on the PS surface. Additional AES, elipsometric, TSDC methods have been applied to study surface films that play a decisive role in light-emitting properties of PS. The studies were done on the composition of rear surface PS films containing purl silicon mixture of silicon oxides SiOx and carbon atoms as well as the uncontrolled impurities of Cl, F, N, Fe. The research has been carried out on the precipitation of PMA polymer films that can be used for protecting PS surface from atmospheric vapours and gases and also the influence of PMA films on the spectrum of PS photoluminescence has been studied.