By varying the feed ratios of comonomers, butyl acrylate (BA), acrylic acid (AA), and methyl methacrylate (MMA), four acrylate macromolecular modifiers (AC730, AC532, AC235, and AC037) were synthesized by free radical copolymeration in ethnol. The effect of these modifiers on rheological behaviors of ultrafine CaCO3 aqueous suspensions was investigated on the basis of a series of rheological measurements. The results showed that comonomer compositions and amounts of modifiers have obvious effect on rheological behaviors of CaCO3 aqueous suspensions. In the case of AC730 and 0.2-0.4 parts of AC532, suspensions were pseudoplastic fluids, exhibiting shear thinning behavior; while in the case of AC235, AC037 and 0.6-1.4 parts of AC532, suspensions were dilatant fluids, exhibiting shear thickening behavior. Except the suspensions modified by 1.2 and 1.4 parts of AC730, the rheological data of other suspending systems could be well correlated with Herschel-Bulkley model. Optimum amounts of different modifiers were determined on the basis of rheological analysis, 0.8 parts for AC730, 0.6 parts for AC532 or AC235, and 0.4 parts for AC037.