Penetration and reflection of millimeter waveband electromagnetic waves have been studied for thin film metaldielectric nanocomposite Co-x(Si0(2)) (1-x) materials, in which cobalt nanoparticles are placed inside of 100nm thickness SiO2 film. Microwave properties of nanocomposite samples with different cobalt content have been measured. Measurements are carried out in frequency range from 26 to 38 GHz. The frequency dependencies of transmission and reflection coefficients are obtained. Share of power loss in the samples was calculated. The algorithm for conductivity reconstruction from the transmission coefficient frequency dependence was worked out. It was found that the microwave conductivity arises with increase of cobalt content and differs essentially from dc conductivity.