Abstract: Serpentine is a silicate mineral that contains large amounts of magnesium, and it often coexists with pentlandite. During the flotation process of pentlandite, the floating serpentine will cause the magnesium content in nickel concentrate to exceed the standard, leading to pentlandite smelting difficulty. In the paper, the crystal structure and surface property of serpentine were introduced, and the reason that serpentine was difficult to be depressed in the flotation was analyzed. In addition, the depressing mechanism of common organic reagents, such as carboxymethyl fiber, starch, chitosan, guar gum, and combination reagents of serpentine were summarized.