In the laboratory, dynamic experiment equipment for simulating on—site flow state is adapted to simulate the operating conditions of surface gathering and transportation system in NY Gas Field with high H₂S and CO₂ content, weight loss coupon, metallographic microscope and SEM and EDS are applied to analyze the effect of liquid flow rate velocity on corrosion inhibitor CP 50. The corrosion inhibitor can well inhibit uniform corrosion and pitting in L 360 NC pipeline steel if its critical flow velocity is the experimental virtual velocity, that is, 8m/s. With the further increase of flow velocity inhibition effect decrease in high flow velocity liquid, which will easily result in pitting, accordingly, inhibition effect decreases significantly. Therefore, it is suggested that pipeline cleaning is conducted periodically so as to minimize the accumulated liquid and suitably control liquid flow velocity.