Surface-modification of fine red iron oxide pigment was carried out in an aqueous solution of sodium poly-acrylate. The sedimentation time of modified samples in water increased from 1.05 to 264.4 hours while the particle size (d50 ) decreased from 1.09 to 0.85 mm, and the tinting strength increased from 100 to 115. The surface-modification as well as the dispersing and stabilizing mechanisms in aqueous solution of the samples were studied by means of IR, Thermal analysis and Zeta potential. The results showed that the modifier molecules acted on the surface of the particles by chemical and physical adsorption, and after the particles were dispersed in aqueous solution, endowing the particle surface with a relatively high negative Zeta potential, thus enhancing electrostatic and steric repulsion between particles for their effective stabilization. Surface-modification of fine red iron oxide pigment was carried out in an aqueous solution of sodium poly-acrylate. The sedimentation time of modified samples in water increased from 1.05 to 264.4 hours while the particle size (d50) decreased from 1.09 to 0.85 mm, and the tinting strength increased from 100 to 115. The surface-modification as well as the dispersing and stabilizing mechanisms in aqueous solution of the samples were studied by means of IR, Thermal analysis and Zeta potential. The results showed that the modifier molecules acted on the surface of the particles by chemical and physical adsorption, and after the particles were dispersed in aqueous solution, endowing the particle surface with a relatively high negative Zeta potential, thereby enhancing electrostatic and steric repulsion between particles for their effective stabilization.