Based on the analysis on the essential characteristics of the typhoon 0414, Rananim, with the aid of weather dynamical method, in combination with the diagnose of meteorological physical fields, the meteorological satellite cloud images, the new Doppler radar data and the numerical forecasted data, in this article, the main causes of strong precipitation during the period under the impact of this typhoon have been emphatically discussed. A few forecasting thought and clue brought forward in the article show...