By using of the conventional data and physical parameters provided by the limited area model,according to the principle of meteorology,the causes of the persisting heavy rain process of June 23—28,1999 occurred in Shanghai were analyzed.The results show that the persisting heavy rain occurs in the condition of the large-scale circulation systems remaining anomalous stability and the multi-scale weather systems interacting and standing in a suitable situation.Meanwhile the vapor,dynamic condition and instability energy which play an important role in the heavy rain persistence were also discussed.