A series of negatively charged macromolecules (NCMs) including poly (sulfonated styrene-co-methyl methacrylate) (P(SS-co-MMA)), poly (acrylic acid-co-methyl methacrylate) (P(AA-co-MMA)) and poly (sulfonated styrene-co-acrylic acid-co-methyl methacrylate) (P(SS-co-AA-co-MMA)) are synthesized by reversible addition fragmentation chain transfer (RAFT) polymerization using carboxyl-terminated trithiocarbonate as a RAFT agent. Activated partial thromboplastin time (APTT) tests indicate that the NCMs can retard blood clotting due to the negatively charged groups. The synthesized NCMs can be blended with polyethersulfone (PES) in dimethylacetamide (DMAC) to prepare membranes by means of a liquid–liquid phase separation technique. The prepared membranes were regular and smooth, except P(AA-co-MMA) modified membranes which were crude and rough due to the poor miscibility of AA segment and PES. The NCM modified PES membranes exhibited good anticoagulant ability due to the existence of the large density of the negative charges on the membrane surface, which induced a strong electrostatic repulsion with the negatively charged blood constituents. Therefore, the P(SS-co-AA-co-MMA) was designed and prepared with appropriate proportions of SS, AA and MMA for better membrane performance. The results indicated that the P(SS-co-AA-co-MMA) had potential to improve the anticoagulant property of biomaterials and to be applied in blood purification.