Abstract: Affected by the northeast cold vortex, there were two squall line processes entering the Bohai Sea on the west coast successively on the night of June 12, 2022. The first squall line weakened rapidly after entering the sea, while the second squall line maintained its intensity and increased slightly after entering the sea. This study used data from the ground automatic stations observation data, Doppler weather radar data, Tianjin Meteorological Tower data, ERA5 reanalysis data, the RMAPS-NOW system analysis data and other multi-source data to compare and possible causes of the different intensity changes of the two squall lines after entering the sea. The results indicate that the intensity difference between the two squall lines after entering the sea is a combined result of multiple factors. The stronger the storm structure of the squall line before entering the sea, the smaller the distance from the main body of the squall line to the gust front, which is more conducive to the maintenance of the squall line after entering the sea. The wet tongue extending from the ocean to the inland, the transition to a convergence flow field on the front side, and the sustained strong environmental vertical wind shear and the convective available potential energy provide favorable mesoscale environmental conditions for the squall line to maintain its intensity. The ascending motion formed by the inflow on the front side of the squall line and the outflow from the cold pool on the rear side closely adheres to the main body of the squall line, which is conducive to continuously transporting warm and humid airflow to the edge of the main body and lifting it, allowing the convective available potential energy to be fully released, thereby promoting the vigorous upward development of the storm structure. In addition, the interaction between the intensity (propagation speed) of the squall line"s own cold pool and the vertical wind shear in the lower environment when it enters the sea is also one of the important reasons for the different intensity changes of the squall line after entering the sea. Approximately equally enhanced cold pool and environmental vertical wind shear are conducive to the maintenance of the squall line.