The invention discloses a preparation method of anion polyamide masterbatch and fibers. The preparation method comprises: dissolving polyamide to obtain a polyamide solution; uniformly dispersing anion powder in the polyamide solution to obtain a mixed liquid; spraying the mixed liquid to pass through a high-voltage electric field, collecting the resulting powdery or fibrous polymer and drying the polymer; mixing the dried anion polyamide powder and polyamide, and granulating to obtain anion polyamide masterbatch; and directly using the masterbatch for melt spinning or blend whole spinning to obtain anion nylon fibers. The anion polyamide masterbatch prepared by the preparation method disclosed in the invention has uniform dispersion of anion powder, and can maximally maintain the separate dispersion state of nano-powder particles in the solution. The obtained masterbatch can be processed into fibers by conventional methods, without the need for equipment alteration and with low wear to equipment.