Thermodynamics for reduction of molybdenum oxidesbyaluminum andsilicon were calculated, andthe results show that reduction reaction is feasible at a certain temperature region. Compared to the presence of CaO or CaCO3, reduction products of molybdenum trioxide with aluminum and silicon at various temperatures were detected by X-ray diffraction (XRD). Results show that molybdenum trioxide is reduced by aluminum or silicon step by step, and the intermediate product is MoO2. At 1000 ℃, molybdenum trioxide could be reduced to metal Mo by aluminum, and in the presence of CaO, metal Moasthereductionproductappearsevenat800 ℃.Incontrast, silicon could barely reduce molybdenum trioxide to metal Mo even at 1200 ℃. In the presence of CaO or CaCO3, reducibility of silicon increases significantly, and the reduction products are metal Mo and MoSi2. Altogether, CaO or CaCO3 performs two major roles in reduction process: restraining sublimation of MoO3 and decreasing the temperature of reducing MoO3 to metal Mo.