Abstract: As for a submarine gas-liquid mixed pipeline, the liquid flow rate at the inlet is high and the structure of downward inclined pipeline-riser is special, so the operational parameters of pigs and the flow parameters of the fluid inside the pipeline fluctuate greatly in the process of pigging. In this paper, according to the pigging process of submarine gas-liquid mixed pipeline, the pipeline was reclassified into four regions based on the Minami pigging model, i.e., the upstream two-phase flow region, the pigging region, the liquid plug region and the downstream two-phase flow region, and their corresponding transient flow models were established respectively. The transient flow model of each region was coupled to simulate and calculate the relevant parameters in the pigging process of submarine gas-liquid mixed pipelines. Finally, the accuracy of this model was verified by taking an actual submarine gas-liquid mixed pipeline in Bohai as a research object, and the variation laws of the pigging operation parameters and fluid flow parameters in the process of pigging were analyzed. The research results are conducive to improve the pigging efficiency and provide the guidance for the preparation of reasonable pigging plans and the efficient and safe on-site pigging operations.