After years of the Wenchuan earthquake took place in 12 May, 2008, rainfall has been the most major triggering factor of geohazards in the earthquake stricken areas. As a random event, geohazards including landslides and debris flows occurrence are affected by environmental factors and triggering factors, as a result the hazard degree should be a variational value varying from the regional random precipitation triggering factor and regional geohazards susceptibility assessment environmental factors. According to geohazards mechanism, the probability based method of assessing the variational hazard degree of regional geohazards is proposed by the combination of probability of daily precipitation and susceptibility assessment. The prediction model is established by the analysis of geology and hydrology factors of the study area, which is incorporating with the analysis of geohazards occurrence data and the corresponding precipitation data. Then, the method is applied in earthquake region of Chengdu City, 8 km away from the epicenter of Wenchuan earthquake, Sichuan province. The validity of the prediction method is verified by evaluating the hazard degree of regional geohazards in Chengdu city on September, 24, 2008 and July, 17, 2009. It is found that the occurrence location and occurrence time of the two geohazards from prediction coincide with those from measurement. As a result, this variational hazard degree assessment model for regional geohazards demonstrates a useful application of a new predictive method and provides a basis for the prediction of time and space of regional Rainfall-induced geohazards.