By employing Reversible Addition-Fragmentation chain Transfer (RAFT)-controlled polymerization, amphipathic random copolymers were prepared. The hydrophobic monomer used was styrene (St), and hydrophilic one maleic anhydride (MA). The resulting copolymers were characterized by Fourier transform infrared spectroscopy (FT-IR). Molecular weight and distributions were determined using gel permeation chromatography (GPC). Macro-RAFT copolymers had the clear advantage of carrying living ends, which allow further chain extension via the addition of desired monomers at controlled rates.With hydrophobic and hydrophilic units, the macro-RAFT copolymers have the potential ability to disperse pigment. Organic phthalocyanine blue pigment (P.B.15:3) was dispersed with the macro-RAFT copolymers by vigorously stirring and ultrasonic processing. The properties (particle size, polydispersity index) of pigment dispersions were measured. It was shown that the particle size and distribution (PDI) has relationship with ultrasonication time and the amounts of macro-RAFT copolymers. The results showed that the particle size and PDI of pigment dispersions dispersed with macro-RAFT copolymer were smaller than that of dispersed with sodium dodecyl sulfate (SDS).