Impurity states in Si/SiO2 structure have been studied using cathodoluminescence (CL). It has been found that intrinsic structure defects in Si/SiO2 are sensitive to the action of magnetic field, which can be revealed due to changes in Si/SiO2 optical properties. The most sensitive to magnetic field (about 35 per cent) is the intensity of the 1.9 eV CL band attributed to non-bridge oxygen atoms.