Henan Province is located in the north-south climatic transitional zone with frequent flood and drought disasters. The risk probability of flood and drought disasters in Henan Province were researched with comprehensive utilization of disaster data and information diffusion model from two aspects of disaster-produced and disaster-consequence, so as to provide a theoretical basis for strengthening flood and drought risk assessment and management. The results showed that: 1) during the period of 1988－2007, the flood years are mainly 2003, 2000, 1998, 1996 and 2005, and the drought years are 1997, 2001, 1999, 1992 and 1988. 2) When the rainfall anomaly percentage were at 20%, 30% and 40%, the floods probabilities were 0.10, 0.06 and 0.04; when the rainfall anomaly percentage were at-20%,-30% and-40%, the droughts probabilities were 0.13, 0.07 and 0.03. 3) When the disaster occurrence rates of floods were 5%,10%,15%, the risk probabilities were 0.81, 0.54, 0.35 respectively, that was 1-3 a encounter, and when disaster rate was greater than 20%, approximately 4.5 a encounter; while the disaster rates of droughts were at 5%, 10%, 15%, 20%, 25%, the risk probabilities were respectively 0.87, 0.72, 0.58, 0.47, 0.38, and that were 1.2 a, 1.4 a, 1.7 a, 2.1 a, 2.6 a encounter. 4) The droughts occurred more frequently than the floods in Henan Province. There was a larger regional difference in space, both flood and drought high risk zones were mainly in Zhumadian, Nanyang, Pingdingshan, the regions with higher drought risk than floods were mainly in Sanmenxia, Luoyang, Zhengzhou, Jiaozuo, Anyang, Xuchang, and the regions with higher flood risk than drought were mainly in Xinyang, Luohe, Kaifeng, Shangqiu, Zhoukou, Puyang, in addition, the regions with both small flood and drought disasters risk were in Jiyuan and Hebi.