The problem of thresholds' uncertainty in satellite cloud imagery classification has been resolved using a technique based on the information of image entropy.Based on the Kapur technique of image entropy,the cloud imageries are classified into several kinds automatically.And the nine thresholds selected as the classification results are analyzed.With the nine thresholds,the cloudy imageries are classified into ten cloud layers.And the cloud classification method is realized.During the storm rainfall of the first ten days of July 2007 in Huaihe River Basin,the method is applied and the results are compared with the enhancement technology of infrared image in GOES User's Guide.The results show that the method is useful for analyzing ground precipitation based on satellite image.