Abstract: Aluminium nitride-molybdenum ceramics with Y₂O₃ additive were prepared via hot-pressing in N₂ atmosphere at 1800～1900℃. The phase constitution and microstructure were detected by XRD and SEM. The electrical resistivity and microwave attenuation property were characterized by the four point valves technique and microstrip line method. The results show that, in the 2～20 GHz frequency region, when the content of Mo is between 4. 56 vol %～15. 03 vol %, the composites present wide-band at tenuation and with the increase of Mo content and sintering temperature , the at tenuation increases ; when Mo content is between 16. 18 vol %～24. 88 vol %, the materials show narrow-band at tenuation under 6, 10, 14, 18 GHz. According to the percolation model, the fitting curve of electrical resistivity indicates that the percolation threshold V_c of Mo is 14. 87 vol % and the corresponding resistivity of the composite is 11. 59 Ω·m. The attenuation characteristic transfers from wide-band to narrow-band as the volume fraction of Mo is above V_c.