Abstract: Surface magnetization of hematite in pulp with synthetic Fe₃O₄ magnetic nanoparticles which were formed in the method of oxidation precipitation by air method in pulp and were coated on the surface of hematite.Then adopt the method of magnetic separation for recycling.The experimental results showed that this method can greatly improve the recovery rate of hematite magnetic separation.Selective separation of hematite from quartz can be realized when ammonia 0.2mol/L,the pulp temperature of 70℃,pH=8,3kg/tmagnetic particles,10kg/t sodium oleate.Through quantitative analysis EDLVO energy between particles to preliminary explore action mechanism and determine the effective magnetization of magnetic nanoparticles and mineral grains range of 0~50 nm.