Abstract: The beneficiation index of conventional low intensity magnetic separation is poor in treating a micro-fine disseminated and low grade magnetite ore from Gansu. To improve beneficiation effect and increase separation index，dispersion-selective flocculation conditions research before low intensity magnetic separation was studied，and the dispersion-flocculation effect were determined with laser particle size analyzer. The results showed that：iron concentrate with iron grade of 62.82%，iron recovery of 79.12% was ultimately obtained with first stage grinding fineness of -74 μm accounted for 90.43%，second stage grinding fineness of -30 μm accounted for 93.45%，low intensity magnetic separation one with sodium hexametaphosphate as dispersion of 500 g/t，carboxymethyl starch(CMS) as flocculation of 750 g/t，pulp pH of 11，via grinding 1-low intensity magnetic rough separation-grinding 2- two times low intensity magnetic cleaning separation process，the grade and recovery of iron concentrate increased by 1.28 and 5.08 percentage points compared with the conventional low intensity magnetic concentrate. Dispersion-flocculation mechanism analysis showed that：little absolute value of surface charge compared with quartz makes Polymer CMS adsorbed on the surface of magnetite by hydrogen bond in dispersion condition，which lead to increased particle size of fine magnetite ore，improve the magnetic separation effect and the beneficiation indexes.

Key words: Micro-fine disseminated magnetite, Dispersion, Selective flocculation, Low intensity magnetic separation