Abstract: Four exceptionally serious r ainstorm events occured in North China and Liaoning Province, namely the "58.7","63.8"."75.8" and "30.8" rains. With a review of their meteorological background and possible causes, this paper points out that the specific disposition of three different synoptic systems of tropical, subtropical and westerly belts causes the meeting of the air current of Warm-wet and cold-dry in this area, and this lend of disposition of the synoptic systems is closely related to the specific superposition of tide-forming force resonance. Especially, if the rainstorm synoptic situation dominates in North China, with a continuously meeting of the superposition of pressure decrease of tide-forming force resonance, it can trigger off an exceptionally serious rainstorm. Concretely, when a typhoon affects this area (assuming that the typhoon intensity is 35m/s at landing the Chinese Continent), the daily maximum rainfall could reached about 500mm if the pressure decrease of one tideforming force resonance occures, and the daily maximum rainfall could reached about 1,000 mm if the superposition of pressure decrease of two tide-forming force resonance occures during the period of a day.