Abstract: To realize the selective flocculation,good dispersion is the important precondition.In this paper,research the influence of sodium hexametaphosphate,sodium silicate,sodium polyphosphate on the micro-fine hematite and quartz sedimentation rate.When pH was 10.5,adding 50mg/L of sodium hexametaphosphate,the sedimentation rate of hematite reduced to 64.32%,and the sedimentation rate of quartz was 38.91%,the difference value between them was 25.41%.Under this condition,the zeta potation of hematite was-29.31mV,sodium phosphate ionized anionic in the water,and the anionic increased electrostatic repulsion and generated the space steric repulsion between the particles,so when the distance between the hematite particles was greater than 12nm,hematite can steadily disperse,the phenomenon conform to the extended DLVO theory.