Abstract: Aiming at the problem of the deterioration of flotation index caused by the entraining of un⁃ derground filling materials into the raw ore in a copper-sulfur mine，a systematic experimental study on the influence of filling materials on copper-sulfur separation was carried out. Through the chemical multi-ele⁃ ment analysis of the raw ore and the filling material，it is found that the content of CaO and MgO in the fill⁃ ing material is high，which will significantly increase the pH value of the pulp and deteriorate the flotation environment. The optimum pulp pH value，collector type and dosage，inhibitor type and dosage of flotation were determined by condition test. The closed-circuit test results show that when the filling material is mixed with 5%，the copper recovery rate decreases by 3.477 percentage points，and the copper concentrate grade and sulfur recovery rate also decrease. Filling material has a significant negative impact on copper-sul⁃ fur flotation，and controlling its mixing ratio within 3% can effectively alleviate the fluctuation of indicators. The research results provide a reference for on-site production adjustment.

Key words: filling material, copper-sulfur separation, flotation, recovery rate