Four kinds of anionic modified copolymer dispersants were prepared by redox-initiated free radical copolymerization with acrylic acid as main monomer and maleic anhydride, acrylamide and hydroxyethyl methacrylate as modified monomers. Ultrafine TiO₂ was dispersed by four polymers. Compared with the results of viscosity, particle size and SEM of TiO₂ suspensions, polyacrylic acid-acrylamide-hydroxyethyl methacrylate (PAA-AM-HEMA) shows the best dispersion effect among all dispersants. The NMR analysis results reveal that the monomer unit composition of the polymer is n(AA)∶n(AM)∶n(HEMA)=14∶1∶2.7. The dispersant contains 79% carboxyl group, 5.6% amide group and 15.4% hydroxyl group. The optimum amount of the dispersant is 0.5% (mass ratio of dispersant solids/titanium dioxide) which can reduce the viscosity (250 mPa·s) of TiO₂/DP4/H₂O (DP refers to polymer dispersant) to 0.5% of the initial viscosity of TiO₂/H₂O. The particle size of TiO₂ dispersed in TiO₂/DP4/H₂O is reduced to 0.06% of the initial particle size (28600 nm) of TiO₂/H₂O. DP4 shows significant dispersion consequent and high efficiency, which is attributed to the steric hindrance effect of the anion content, hydrogen bonding and hydrophobic functional groups in the acrylic anionic copolymer structure. The copolymer structure just contributes to the stability of the electric double layer structure.