The results of an investigation of the point defects generation, redistribu¬tion and interaction with impurities in the Si-SiO2 system during the process of its formation by means of EPR spectra are presented. It has been shown that the type and density of the point defects in the Si surface layer depend on the oxidation condition: temperature, cooling rate, oxidation time, impurity content. Interaction between the point defects and impurities were studied on powdered and crystalline samples. Samples powdering allow to increase its surface and discriminate the point defects interaction with impurities on the surface and in volume. The oxides were thermally grown in dry or in wet oxygen. Non-oxidized Si powders have an intensive EPR signal at g=2.0055 due to broken Si valence bonds. After the oxidation this signal vanishes and a new but weak signal at g=2.000 (I) arises. This signal increases with an oxidation temperature, whereas it is stronger when oxidation were carried out in dry oxygen. After etching the oxide the EPR signal diminish its value. It confirms that centers formed by high temperature oxidation are localized both in Si and in SiO2. The activation energy of paramagnetic centers is determined from the I(l/T) dependence is 3.5 eV. The activation energy of vacancies is 2,5 eV, the binding energy of divacancies is 1.6 eV and the creation energy of divacancies E= 2,5x2-1,6=3,4 eV, that coincide with the experimentally obtained value. The revealed difference between interface properties of n- and p-type wafers are connected with different Fermi level position at the interface and different point defects density in volume near the interface.