Modified waterborne poly(methacrylic acid) (MPBMA) with hydrophilic and hydrophobic groups is prepared by reacting maleic anhydride/polyglycol, alpha-olefine benzenesulfone, and methyl methacrylate. Using MPBMA as a ceramic dispersant, the effects of the MPBMA concentration on the rheological behavior of a ceramic suspension and the ceramic breaking strength are studied, and the reasons and its dispersing mechanism are analyzed. The results show that MPBMA can improve the suspension's rheological properties and enhance the ceramic strength. The optimum copolymer concentration is 0.20 wt % at pH 9-10. When adding 0.20 wt % MPBMA, the suspension's absolute zeta potential increases from 23.7 to 64.2 mV, and its zero shear viscosity decreases from 714.3 to 73.4 mPa s. At the same time, its thixotropy area reaches the minimum, and the suspension exhibits Newton flow behavior and good dispersivity. Compared with inorganic dispersant, the ceramic with added MPBMA has higher breaking strength, which is increased from 160 to 352 MPa. Scanning electron microscopy photographs show that the flocculate of particles is disintegrated and the particles scatter mutually. They also show that no aggregation phenomenon appears in the ceramic with MPBMA added and the pores distribute uniformly. (c) 2006 Wiley Periodicals, Inc.