A water-soluble copolymer of maleic acid (MA) and sodium methallyl disulfonate (SMADS) were synthesized by aqueous solution free radical polymerization and evaluated as scale inhibitor for barium sulfate. The copolymer was characterized by FTIR, HNMR, GPC and HPLC results verified the structure of MA-SMADS copolymer and molecular weight was about 1050 g/mol. The experimental results indicates that the optimal conditions for copolymer synthesis are 105 °C, monomer dosage 30% (wt) and sodium persulfate (NaPS) dosage 7%. The inhibition performance of polymer on barium sulfate was evaluated through static bottle test and the static inhibition rate on barium sulfate can reach up to 98%. Consequently, the evaluation criteria was carried out by dynamic scale loop test.