Abstract: The article discusses the relation between tl:e fluctuation of the cereal's gibberellin prevalence in the middle and lower reaches of the Chang-Jiang and the weather factors. It is found through statistical analysis that wheat groberelfin and bareiey gibbcrellin development in the whole region are corrciamd, with similar speed and stage, while winter wheat is more susceptible to it.The warm moist and rainy weather during the blooming period is the major cause leading to the fluctuation of the gibberellin prevalence. And the similarity of weather in the wl:oie region in the large scale weatiicr pattern causes the common trend of the dissease.Thus the forecast of gibberellin prevalence can be made either from the weather in blooming period or the change of weather patterns to provide the basis for the prevention and avoiding of cereal diseases.