Abstract: Huge dosage of sodium silicate makes the tailing water unsinkable and recycled water can’t be reused in molybdenum ore practice processing. For this problem, classification floatation is discussed in this paper. After crushing and grinding, explorative tests are carried out to determine the optimum classification size: +0.037mm and-0.037mm. Then we carry out flotation tests receptively and the molybdenum grades of concentrate are 51.9% and 47.3%，recoveries are 96.21% and 92.66%. Compared with two flotation results, we find that sodium silicate dosage with classification flotation is less than flotation without classification. Moreover, contrast tests on tailing sedimentation show that the problem of tailing difficult settlement is obviously improved with classification flotation.