The invention belongs to the field of positioning hard coatings on metal material surfaces, and particularly relates to a preparation method for a chromium nitride (CrN) coating. The method is characterized in that in an electric-arc ion plating process, one axial magnetic field coil is applied to the outer side of a cathode Cr target, so that axial magnetic fields generated by the axial magnetic field coil carry out constraint control on arc spots; and velocity of movement of the arc spots is accelerated to deposit a high-quality CrN coating on the surface of a basal body, so that the Cr coating with relatively high hardness, high toughness and a relatively low friction coefficient is obtained. The preparation method is suitable for depositing the CrN coating on surfaces of various tools, moulds and metal parts, so that performances of workpieces are further improved, and service lives of the workpieces are further prolonged.