Abstract:Basic theory of extension method is introduced in this paper. It can be applied in geological hazard probability of occurrence assessment. Selecting rock soil mass types, hill slope, geological structure, the number of disaster, intensity of human engineering activity and multiyear average precipitation as the evaluation indexs, using the method of analytic hierarchy process for weight value, susceptibility evaluation model has been established based on extension theory of geological disaster. Taking Ji'nan city as an example, the extension evaluation model is used to validate the results. The results obtained by using this method can agree with the actual situation highly. It is proved that this method is feasible.