Polymer corrosion inhibitors have many advantages in comparison with small organic molecule inhibitors, such as easier formation of multilayer films on metal surface, more adsorption sites and better temperature resistance. Poly(maleic acid-co-N‐[3‐(dimethylamino)propyl]‐methacrylamide) (PMD) was synthesized via aqueous solution polymerization and its structure and molecular weight were confirmed. The anti-corrosion performance of PMD for Q235 carbon steel in neutral medium was evaluated by several methods like gravimetric and electrochemical tests, surface analysis and theoretical calculation. Results indicated that polymer corrosion inhibitor PMD exhibited high corrosion inhibition efficiency of 90.1% at a dosage of 200 mg/L, and acted as anodic-type inhibitor that inhibited anodic reactions by forming adsorption polymer film. The adsorption model conformed to Langmuir adsorption isotherm involving both physisorption and chemisorption fitted by electrochemical data. The outcomes of surface morphology investigation including contact angle analysis, AFM and SEM were consistent with experimental results. Moreover, Theoretical calculation including quantum chemical computation and molecular dynamics (MD) simulation further reveal the corrosion inhibition mechanism of PMD.