Using the mesoscale TJWRF model data and encryption automatic weather station (AWS) data, etc., we analyze the distribution characteristics of Tianjin urban heat island circulation and sea breeze circulation as well as the interaction of them. Through several typical weather cases (Local strong thunderstorms seen in urban areas and the weather without any processes affected by the sea breeze), the trigger mechanism of the interaction between urban heat island circulation and sea breeze circulation for local thunderstorms is analyzed. The results show that the extended height of urban heat island circulation is near 800 hPa, spatial extention is about 20 km, and the upward motion is obvious. The extended height of sea breeze circulation is near 800-750 hPa and spatial extention is about 40-60 km. The stretch height of the sea breeze front is about 950-900 hPa in the forefront of the sea breeze circulation, and the upward speed is 0.2 m·s-1 on average, slightly stronger than the heat island circulation. The sea breeze can weaken the urban heat island effect while the urban heat island can block the sea breeze circulation. With the sea breeze circulation pushed near to the urban, the sea breeze circulation and the urban heat island circulation encounter, then the two circulations get superimposed and the upward motion is significantly strengthened, causing the maximum upward speed to go up to 0.6 m·s-1. Under the favorable weather conditions the local severe thunderstorms can be triggered.