Abstract: Using conventional observation data, radar data, and ERA5 reanalysis data, combined with two different evolution characteristics of strong convection cases in the Bohai Strait in 2021, this study analyzes the impact of the underlying surface on the intensity of linear storms. The results show that both the strengthening and weakening processes occur under the influence of weak weather scale systems, and both processes are accompanied by a warm temperature ridge at the lower level, which is conducive to the establishment of potential instability stratification. At night, when the weak weather system affects, the thermal circulation and dynamic forcing caused by the uneven temperature of the underlying surface play a major role, while the role of the underlying surface caused by sea surface temperature differences is secondary. In general, when linear convection moves eastward to the Bohai Strait at night, it is weakened by the divergent airflow over the cold water area in the Bohai Strait. When the ascending motion in the near-sea layer caused by uneven underlying surface temperature is superimposed with environmental convergence, the storm is enhanced. In this case, there is a relatively shallow mesoscale secondary circulation of ascending warm water areas and descending cold water areas in the near-sea layer near the Bohai Strait. Environmental convergence is often caused by outflows of other surrounding storms that are lifted by environmental wind convergence. Additionally, environmental easterly airflow and strong vertical wind shear at 0-1km are conducive to maintaining the ascending motion of linear storm movement; sea breeze and coastline curvature also have an impact on coastal convection.