Water was used as solvent and allyloxy polyethoxy sulfate（APES），maleic anhydride（MA），polymer of maleic anhydride and acrylic acid（MA-AA）were used as monomers to synthesize phosphor-free scale inhibitor and the copolymers structure was characterized by means of FT-IR and 1H NMR.Free radical polymerization of APES with MA and graft polymerization of APES with MA-AA happened simultaneously.APES-co-MA was the main product while（MA-AA）-g-APES was the minor product.The influence of monomer ratio，dosage and temperature，viscosity-average molecular weight on the copolymers scale inhibition performance was discussed，and the results showed that the copolymer not only had excellent phosphate inhibition capability but also had good carbonate inhibition capability.Its phosphor inhibition reached 98.89% when dosage was 5 mg·L-1 and temperature was 80℃，and reached 100% when dosage was 5 mg·L-1 and temperature was 50℃.Carbonate inhibition reached 97.97% when dosage was 25 mg·L-1 and temperature was 50℃.The calcium carbonate was easy to get rid of，because it became fluffy.The copolymer is suitable for general industrial cooling water system.