The CaCO 3 deposits exist widely in the petroleum industry, causing severe damage to the equipment and production. In this article, a novel environment-friendly terpolymer scale inhibitor Poly (maleic anhydride -acrylic acid -2-acrylamide -2-methyl propanesulfonic acid) (P(MA-AA-AMPS))-containing carboxylic acid group, sulfonic acid group, and amide group was synthesized. The structure and molecular weight were characterized by FTIR, 1 H-NMR, and GPC. The static scale inhibition experiment was conducted to study the influence of factors such as the dosage, monomer ratio, temperature, pH, Ca 2+ concentration, and HCO − 3 concentration on the scale inhibition performance of CaCO 3 . The results show that when the monomer ratio is 2.0:1.0:0.5 and the dosage is 20 mg L −1 , the maximum scale inhibition efficiency is 95.52%. Even when Ca 2+ concentration exceeds 1200 mg L −1 and temperature reaches 90 C, the scale inhibition efficiency is still larger than 80%. The results of SEM and XRD show that P(MA-AA-AMPS) interferes with the growth of CaCO 3 crystal by adsorption, dispersion, and chelation. The effect leads to changes in the morphology of CaCO 3 crystals, the size of which drops from 20-30 μm to 2-5 μm. The P(MA-AA-AMPS) can transform CaCO 3 from stable calcite crystals to unstable aragonite and vaterite. Finally, the formation of CaCO 3 scale is well inhibited.