Abstract: Subsea pipeline is the aorta of oil and gas production system in the development of offshore oil and gas fields. Problems such as liquid accumulation are easy to occur inside the subsea pipeline, which lead to the increase of pressure difference, even the decrease of the transportation efficiency of the pipeline with the great risk.Therefore, in view of the continuous increase of the pressure difference of the pipe between the B platform and the A platform in a gas field, the factors that may cause the increase of the pressure difference (including scale formation, effusion and hydrate formation) are analyzed in combination with the data of pressure, temperature and transport volume of the sea pipe monitored in real time. Finally, it is determined that the inducement of the continuous increase of the pressure difference of the sea pipe is the effusion. To ensure the safe and efficient operation of the offshore pipeline, a pig is immediately launched from Platform B on site, effectively resolving the liquid accumulation issue in the pipeline. The pressure differential in the pipeline is promptly restored to normal. This practical study provides valuable insights for addressing similar issues of increased pressure differential in offshore pipeline transportation.