Abstract: In order to test the effectiveness of the new inhibitor of HEC and the influencing factors for the effect of HEC，the flotation tests of chalcopyrite and pyrite pure mineral were carried out with butyl xanthate as collector.And flotation tests for the real minerals were conducted with HEC as the inhibitor.The results show that:①Butyl xanthate has a stronger collecting ability on chalcopyrite than that on pyrite and is hardly affected by the pH value of the pulp.In the absence of inhibitor，the floatation of pyritecan was inhibited in the high alkali environment.②HEC can be used for separation of copper and sulfur.When the dosage of HEC is 200 mg/L，pyrite can be obviously inhibited，but chalcopyrite is opposite.③suitable pH value for flotation separation of artificial mixed ore of chalcopyrite and pyrite is 7 with HEC as an inhibitor.④In the separation of a copper and sulfur ore in Inner Mongolia，using HEC as inhibitor of pyrite for separating copper and sulfur，a copper concentrate with a copper grade of 23.21% and a copper recovery of 81.75%，and a sulfur concentrate with a sulfur grade of 13.20% and a sulfur recovery of 80.83% were obtained with separation of copper and sulfur better achieved.

Key words: Chalcopyrite, Pyrite, New efficient inhibitor HEC, Cu-S separation