Based on analysis data of EC numerical model, real-time observation and statistical calamitous data, a synoptic analysis of the weather and the circulation situation in 2004 is made. The result shows that the continuous drought happened in North China, Northeast China and South China is closely related to the abnormal of the synoptic circulation. The interaction of the synoptic system under the favorable situation resulted in the calamitous weather such as heavy rain, thunderstorm and sandstorm etc. Having a good understanding of the synoptic situation and evolution character of the affecting weather system is very important to improve forecast accuracy of the calamitous weather and the disaster prevention.