A terpolymer ESA/IA/SS was synthesized by copolymerization using epoxysuccinic acid (ESA), itaconic acid (IA) and sodium p-styrenesulfonate (SS) as monomers and ammonium persulfate as initiator. The structure of product was determined by IR. In addition, the effects of mass radio of MA and IA, initiator amount, reaction temperature and reaction time on the properties of the polymer. And The optimal synthesis conditions was obtained. when the m(MA):m(IA)=3:1, the amount of SS and initiator accounted for 20% and 12% of the total monomers mass respectively, the reaction temperature was 85 oC and the reaction time was 4 h, the viscosity average molecular weight of the product was 1176.3. The properties of scale inhibition and dispersion of ESA/IA/SS were studied and compared with those of ESA/SS and PESA. The results showed that the property of inhibition to CaCO3 scale of ESA/IA/SS was similar to that of PESA. When the dosage was 50 mg/L, the scale inhibition rate of PESA was 72.3%, and that of ESA/IA/SS was 71.5%, which was 27.3% higher than that of ESA/SS. For the property of inhibition Ca3(PO4)2 scale, ESA/IA/SS was much higher than PESA. When the dosage was 40 mg/L, the rate of scale inhibition of PESA was only 7.0%, while that of ESA/IA/SS was 98.6%. Beside, ESA/IA/SS had a certain property of dispersing Fe2O3, the light transmittance of the FeCl3 solution with ESA/IA/SS kept at 72.6%.