The 5.12 massive 8.0magnitude earthquake created enormous devastation and loss of life in Sichuan, China. An assessment method of earthquake affected degree and related regionalization in Beichuan County were put forward, being expected to be helpful to the reconstruction of building and economic development after disaster. According to the system theory of natural disaster, assessment indicator system for earthquake damage in Beichuan was established, which was made up of four levels such as disasterpregnant environment, disastercausing factor, disasteraffected body and situation of disaster. Maps of the degree of sensitivity, risk, and vulnerability as well as the distribution of disaster intensity in study area were obtained by GIS technology, and then were divided into many grid units defined as 1.5×1.8km, respectively, for overlay analysis with MapGIS software. Regionalization of earthquake damage was operated by regioncombined method based on the spatial neighborhood relationship and analysis of diversity of region with secondary geological hazard. 4 earthquakeaffected region types were found in the regionalization map in which the number of very heavy, heavy, moderately and lightly damaged regions were 1,4 ,2 and 2 respectively. Finally, the strategy for reducing disaster risk was discussed.