In this work, the synergistic inhibition behavior and mechanism of magnetic field (MF) and inhibitors against carbon steel corrosion in CO2-saturated oilfield-produced water were investigated using potentiodynamic polarization curves and electrochemical impedance spectroscopy. The results show higher inhibition efficiencies, more than 94%, when inhibitors (imidazoline derivative, dodecylamine, and dodecanoic acid) at low concentrations of 10 mg/L are used in conjunction with 65 mT MF. The corrosion of steel is significantly inhibited in the presence of inhibitors with the assistance of MF. As a result, the inhibition efficiency is significantly improved. The direction of MF relative to the electrode surface has a significant influence on the charged inhibitor but has no influence on the inhibitor with no charge. This paper gives a good direction to significantly increase the inhibition efficiency of inhibitors by using MF in the oil and gas industry.