Abstract: This paper establishes a mathematical model to study the corrosion factors of multiphase flow pipeline for the gathering pipeline in oilfield. 7 factors including flow velocity of medium transported, oxygen content, pH index, salt content, temperature, CO₂ partial pressure and water cut are studied to predict their corrosion impact to ^#20 steel. It is pointed out that the flow velocity of medium transported, oxygen content and bacterium vary in a wide scope, which is a major cause to result in the partial corrosion of gathering pipeline, and the environment with low pH index and high saltiness also speed up the corrosion progress of pipeline.