The main purpose of this work is to explore the erosion-corrosion reduction mechanism under the synergistic action of swirling flow and inhibitor, and to provide theoretical support for the development of new erosion-corrosion control method based on swirling flow. The comparative experiments research of using inhibitor to inhibit pipeline erosion-corrosion under the conditions of liquid-solid non-swirling flow and swirling flow was carried out to evaluate the potential for the synergistic use of swirling flow and inhibitors by using a circulating loop system in combination with weight loss test, electrochemical test, morphology analysis, high-speed photography and XPS corrosion product analysis. The results of weight loss method and electrochemical measurement show that under non-swirling flow and swirling flow conditions, the inhibitor has an effective inhibitory effect on the four components (pure corrosion, pure erosion, corrosion-enhanced erosion, and erosion-enhanced corrosion) of No. 20 steel erosion-corrosion, but the inhibition efficiency for pure erosion is less than the inhibition efficiencies for the other three components. The synergistic inhibition efficiencies of swirling flow and inhibitor on the four components of pure erosion, pure corrosion, corrosion-enhanced erosion and erosion-enhanced corrosion are higher than those of inhibitor on the four components alone. Among them, the synergistic action of swirling flow and inhibitor has the highest inhibition efficiency for erosion-enhanced corrosion component, reaching 93.75%. The results of high-speed camera show that swirling flow generated by the twist tape increases the tangential velocity of the sand and produces the sand particle suspension effect, which improves the distribution of sand particles. It is concluded by microstructural examination that the corrosion product layer on the working electrode surface is the most complete and compact and the number of corrosion pits is the least under the synergistic action of swirling flow and inhibitor. XPS analysis proves that the inhibitor is adsorbed on the electrode surface under swirling flow and non-swirling flow conditions, and swirling flow promotes the mass transfer of dissolved O2 and inhibitor to the electrode surface and the adsorption of inhibitor on the electrode surface. The potential fluid dynamics advantages of swirling flow produce the sand suspension effect and mass transfer enhancement effect which facilitate the adsorption of inhibitor on the working electrode surface and acting in conjunction with the oxide film to form a more complete and dense protective corrosion product layer. This furtherly promotes the inhibition on pure corrosion, pure erosion, corrosion-enhanced erosion, and erosion-enhanced corrosion, and give full play to the inhibition effect of the inhibitor. The synergistic action of swirling flow and inhibitor has potential advantages in reducing pipeline erosion-corrosion.