Abstract: Using MOH as collector, sodium silicate, oxalic acid and LD-C (carboxymethyl cellulose) as depressants, single mineral flotation of ilmenite and pyroxene was carried out. In addition, the interaction mechanism of LD-C with ilmenite and pyroxene was studied by solution chemistry of flotation, zeta potential test and infrared spectroscopic test. The test results show that the selective depression effect of LD-C on pyroxene was significantly better than that of sodium silicate and oxalic acid. Under weak acidic conditions, and the dosage of collector MOH was 160 mg/L, depressant LD-C was 2 mg/L, the recovery of ilmenite can reach 80% and that of pyroxene was 9%. The interaction of LD-C on pyroxene can hinder the subsequent adsorption of MOH while that on ilmenite has little effect on the adsorption of MOH. This due to the fact that the active sites of Ca and Mg exposed on the pyroxene surface during flotation can make LD-C adsorb on pyroxene strongly, which hindering the adsorption of collector.