Road icing is one of the major disastrous weathers in meteorology.Accurately understanding the occurring law of road icing and scientifically forecasting it are the keys to effective disaster prevention and mitigation. Firstly, daily snow depth, daily minimum temperature, daily rainfall amount are taken as the main meteorological factors affecting road icing, and then the problem whether the freezing happened at last is abstracted into the binary classification one. Secondly, C4.5 decision tree algorithm in data mining is adopted to find the classified roadicing forecasting rules that are easily used by forecasters. Finally, road icing rule set is got by carrying out experiment with roadicing sample of data in Lianyungang and Jiading districts from 2004 to 2013. The first eight years' data of Lianyungang regional road icing data samples are used to gain classification rule so as to find four road icing prediction rules fitting Lianyungang district, then the remaining two years' data are used to validate with 96.82% accuracy rate. The same experiment steps are conducted in Jiading area. Three road icing prediction rules fitting Jiading district are got and the validation accuracy rate reaches 94.87%. The above tests show that the road icing forecast model by C4.5 decision tree algorithm can not only predict accurately and easily, but is facilitated directly by forecasters. Meanwhile, each road icing forecast rule is in highly accordance with weather process and theory in meteorology.