Abstract: On August 3, 2014, the earthquake occurred in Ludian county of Zhaotong city, Yunnan province, forming Hongshiyan dammed lakes. It seriously threaten to the upper and lower reaches of Niulanjiang river. It is very important to provide meteorological service of areal precipitation to the emergency rescue for the dammed lakes. In this paper, we introduce the method of boundary extraction and areal precipitation calculation in the upper reaches of dammed lakes in Ludian county, Yunnan province. Then we established a model of areal precipitation calculation by employing GIS geographic modeling techniques. It is found that the process integration and fast calculation may serve to the decision makers for such kind of emergency.