Mo-doped Alumina (Al2O3/Mo) ceramic composites were prepared by powder metallurgical process. The influence of Mo doping amount on the microstructure and electrical properties of the composites were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and other testing analysis methods. The results show that the composites were composed of Al2O3 and Mo phases and without any impurities. When the amount of Mo is below 20wt.%, there are no obvious changes in resistivity (>1012Ω?cm) and permisitvity(8-9) for the composites, but the refaining of grain. When doping amount over 20wt.%, the Mo transforme from dispersed phase into the continuous phase while volume resistivity decrease to 1010Ω ? cm shaply; When doping amount is 40wt.%, since the throughout matrix of Mo is formed, the volume resistivity decrease slow, steady at about 10Ω ? cm. Therefore, by adjusting the amount and phase distribution of Mo in Al2O3 matix, ceramic/metal composite materials with different resistivity can be prepeared.