Abstract: Colemanite surface was modified by wet chemical process with stearic acid and oleic acid as modifiers respectively and with anhydrous ethanol as solvent.The influences of temperature，time，liquid-solid ratio，and dosage of modifier etc. on the modification effect of colemanite were investigated.Unmodified and modified colemanites were characterized by the means of FT-IR，XRD，TG-DTG，and SEM etc..The results demonstrated that the modified colemanite had the optimal performance and its activation index was 99.45%，when colemanite was modified by addition of 5%（mass fraction） stearic acid at 75 ℃ for 75 min with liquid to solid ratio of 2∶1（mL/g）；while the activation index of colemanite modified by 5%（mass fraction） oleic acid at 60 ℃ for 50 min with  liquid to solid ratio of 1∶1（mL/g） was 68.30%.

Key words: stearic acid, oleic acid, colemanite, surface modification