The discharge and storage of carbide slag are increasing year by year, so the utilization of ferrosilicon derived from carbide slag has also become a problem to be solved urgently. For the high-value application of carbide slag ferrosilicon, the heavy medium suspension was prepared using magnetic ferrosilicon separated from dry-process carbide slag, and the effects of suspension density, clay content and ferrosilicon particle size on viscosity and sedimentation characteristics of suspensions were studied. The results show that increasing suspension density or clay dosage and reduces ferrosilicon size increases the viscosity of suspension to reduce the sedimentation velocity of medium solids, and the stability of the suspension is improved. Furthermore, in order to verify the feasibility of using this suspension system for practical separation, the suspensions with different densities are tested in float and sink experiments to separate coal samples. Under the suspension density of 1.30 g/cm3 or 1.40 g/cm3, the floating coal reveal relatively high yield and its ash content significantly decrease compared to initial coal sample, which reflect the great separation performance of this suspension system.