Abstract: Seven typical cases of collision-type sea-breeze front happened in the Bohai Bay region of China, are analyzed with observational (Doppler radar and surface stations) and reanalysis data. The analysis shows that convective systems significantly develop when they hit the sea-breeze front from its front, rather than its rear. A steady upper level westerly favors steering convective systems to move eastwardly and collide with the sea-breeze front. Lower level wind convergence enhances the occurrence of convective motion during the collision, and the water vapor transportation by the flow at the northwest edge of the subtropical high favors the formation of precipitation. The neutral atmospheric stratification at the lower level, caused by a topographic thermal effect, also promotes the occurrence of convective motion. The dynamical effect of topography may enhance the triggering or intensifying nature of the convective systems colliding with the sea-breeze front under the condition of the upper level westerly.