The electrodynamic properties of new composite materials based on AlN and made by the free sintering method, with the addition of diamond powders in the amount of 1-5 wt.% were investigated, in the frequency range of 1-10 GHz. As a result of the studies of the structure and phase composition, it was established by  X-ray phase analysis that during the sintering process, the graphitization of diamond powder takes place, and after refining the results obtained by the Rietveld method, show that the content of the graphite phase was 0.8, 1.7, and 3.8 wt.% for the materials in which added diamond powder before sintering in amounts of 1, 3, and 5 wt.%, respectively. The study of electrodynamic characteristics showed an increase in the imaginary and real values of the dielectric constant with an increase in the graphite content. Dielectric losses at 10 GHz increase from 0.05 to 0.08 for composites as the amount of graphite phase increases from 0.8 to 3.8 wt. %. It is shown that at frequencies from 1 to 10 GHz, the real part of the dielectric constant for composite materials of each composition practically does not change, while the imaginary part increases slightly. At the same time, an increase in dielectric losses with increasing content of the graphite phase was noted in the entire measured frequency range.