Abstract: In order to solve the technical problem that the high content of magnesium oxide in the concentrate affects the subsequent smelting process and the grade of metal recovery in a copper-nickel sul⁃ fide ore，aiming at the problem that it is difficult to separate the magnesium silicate gangue minerals such as serpentine and talc in the concentrate，the beneficiation process test of reducing the grade of magnesium oxide in the concentrate is carried out.The test results show that the flotation process of one roughing，two cleaning and three scavenging，combined with the application of CD-C inhibitor，can effectively inhibit the magnesium-bearing gangue minerals such as serpentine and talc in the concentrate. The content of magnesium oxide in the concentrate is reduced from 12.14% to 5.27%，and satisfactory test indexes are ob⁃ tained. It has important reference significance for similar copper-nickel sulfide ore to reduce magnesium�bearing gangue minerals.

Key words: flotation, magnesium reduction in concentrate, inhibitor, serpentine