This paper presents the study on the corrosion protection of the gathering pipelines in offshore oil fields. The study addresses the issues of high corrosion rate under complex working conditions including high CO2 content, high salinity and high flow rate in an oilfield in the South China Sea. An imidazoline intermediate was synthesized using lauric acid and diethylenetriamine as raw materials in the laboratory. Then a water-soluble thioureido-imidazoline corrosion inhibitor was obtained after thioureid-based modification and combination. According to the working conditions of the oil field in the South China Sea, the static corrosion coupon evaluation experiment was carried out and the product formula was determined. Then, the industrial scale production of that corrosion inhibitor was used to obtain industrial pilot samples. Through the dynamic corrosion coupon evaluation experiment using the two inhibitor product samples from indoor synthesis and industrial scale pilot testing, it is found that the corrosion inhibition rates of the two samples to X65 carbon steel are above 98%. Finally, the product formulated in the industrial pilot test was extended for application to the target oil field, and the average corrosion rate was successfully controlled at about 0.0155 9 mm/a, achieving a good corrosion inhibition effect. It has been proven from actual practices that the water-soluble thioureido-imidazoline inhibitor can tackle the pipeline corrosion in oil fields under such complex working conditions and has a good prospect for wider application.