Abstract: Corrosion problems of gathering and transportation system in Changqing Oilfield had become increasingly serious. The water samples, corrosion products and corrosion rates of different oil well gathering systems in Huanjiang Block and Baibao Block of Changqing Oilfield were systematically studied. The results show that the water samples in Changqing Oilfield gathering system contained a large amount of Ca²⁺, Mg²⁺, SO₄^2- and HCO₃^-. The concentraions of CO₂ and O₂ in the water samples of the gathering system in Huanjiang Block were relatively high, and the corrosion mechanism in Huanjiang Block was mainly resulted from electrochemical corrosion resulted from Ca²⁺, Mg²⁺ and CO₂. Baibao Block gathering system contained a large amount of H₂S, and the electrochemical corrosion caused by H₂S was the main factor leading to the corrosion of the gathering system in Baibao Block.