This paper aims to probe the impact of different methods upon the surface modification of the negative ion powder. Using KH-570 as the modifier, the surface organic modification of the ultrafine negative ion powder is conducted by three methods, including ball milling, solvent reflux and dry milling. The coating of PMMA on the surface of the pre-treated negative ion powder is carried out through suspension polymerization, by dispersing the negative ion powder in MMA monomer, yielding the negative ion powder containing polymeric microsphere. The suspension performance of the powder in MMA monomer is compared using 7230G spectrophotometer; The morphology of the powder and the binding of the powder and the polymer are characterized by SEM; The effective coating rate is calculated by isolating the negative ion powder that is not coated; The release performance before and after polymer coating is tested through COM-3010PRO negative ion detector. The three modification methods are then compared after comprehensive comparison and analysis. The surface organic modification of the negative ion powder can be successfully carried out by all the above three methods; The average particle size of the negative ion powder decreases upon surface modification, which enhances the dispersion stability of the negative ion powder in MMA. The polymer coated negative ion powder can be yielded through suspension polymerization. The negative ion powder can homogeneously distribute in polymer and bind firmly with the polymer. The effective coating rate of the polymer can reach up to 79.2%. After comparing the dispersion stability, polymer coating rate, distribution status and the negative ion powder release performance of the negative ion powder, it concludes that the three modification methods follow the trend:ball milling, solvent reflux, dry milling. The most effective modification method is ball milling. It ensures the homogeneous dispersion of the negative ion powder in the polymer, the high polymer coating rate and high negative ion release amount.