A severe thunderstorm occurred in the north of Zhejiang Province, during the afternoon of July 16 2002. By using of the conventional data and physical data provided by T213 in MICAPS,combined with radar data and satellite cloud image, an analysis of large scale atmospheric circulation and corresponding physical fields associated with this event is made. The results show that the easterly wind in the south side of subtropical high provided plenty of water vapor and energy. In the south of Changjiang River controlled by warm center, it appears high temperature in large range, an atmospheric layer with high temperature and high humidity was formed. In the north cold front and tilted trough, carrying cold air with them, stricked the unstable atmospheric stratification in the northwest of subtropical high, which generated strong convection, triggered the release of unstable energy and provide dynamic lifting for severe thunderstorm.