Abstract: Landslides, debris- flows and collapses are caused by heavy precipitation frequently. A zonation for national geological disaster was carried out, and the 9 regions were divided so called as:the Northwestern China, Northeastern China, Tibetan Plateau, Loess Plateau, Qinba Mountain, Northern China, Yunnan-Guizhou Plateau, Central and South China and Southeastern China. The critically intraday precipitation for geological disaster in China was investigated based on the information of geological disasters in 1950-2014. Based on the Gaussian fitting method, the probability forecast model was adopted to describe probabilistic relation between precipitation and geological disaster. The intraday critical precipitation and forecast indexes of geological disaster were established with the geological disaster risk grades in business. And then this indexes were tested for 172 samples of geological disaster during April to October 2015 in China and samples of Xingguo and Yudu counies in Jiangxi Province during 17 May to 21 May 2015. The practical application has shown that the model has a good effect, the discriminant method of intraday critical precipitation indexes is effective and feasible.