Abstract: Taking the Yulin nenghua-Jiaojiawa trunk CO₂ transportation pipeline in the first-stage pipeline network project of Yanchang oilfield as an example, the impurity water condensation process and its corrosion threat in the actual pipeline network engineering were analyzed in combination with thermodynamics. The OLGA software was used to simulate the water film formation and predicte corrosion threat of the pipeline. The water film content and its position changes under steady-state conditions and different transient conditions were analyzed, and the applicability of the simulation method was verified based on the experimental data. The results show that during steady-state operation, there was a certain volume of continuous water film in the front 22.3 km of the pipeline, and there was a corrosion threat in the pipe. With the fluctuation of pipeline throughput, the volume of water film increased, and the pipe section with water film under low throughput was longer. During the low pressure operation, the volume of water film decreased, but during the pressure recovery process, the volume of water film increased rapidly, and the length of pipeline covered by water film reached 37 km. Under the condition of shutdown/restart, the volume of water film and the length of the pipe section with water film decreased, but the shutdown may lead to the accumulation of static water film in the first 8 km pipeline, resulting in serious corrosion of the pipe wall. Under the leakage condition, the volume of water film in the pipe increased, the length of the pipe section with water film increased to 30 km, and the corrosion threat in the pipe was greater.