The analysis was conducted for two winter thunderstorms on December 21,1990 and December 31,1996 in Shenyang,Liaoning province. The results show that the two winter thunderstorms were due to cyclones explosive developing in short time. The explosive developing cyclones cause both large range of snow in northern area and strong convection weather. Cyclones moved along the path as the letter "U",got into Bohai sea and developed quickly. 850 and 700 hPa high explosive warming and explosive wetting caused potential instable stratification occurrence,they are the key to the winter thunderstorm forecast. In addition,urban heat island effect is very important to trigger off the winter thunderstorm.