Abstract: Earthquake resistance and protection decision making involves a lot of fuzzy information that is very important to the whole analysis. In this paper a methodology to incorporate the fuzzy information into a probabilistic approach to seismic risk analysis and the decision making is proposed, a princIple to model the fuzzy information by fuzzy set is introduced, and a vertex method for interval analysis to further process the fuzzy information is discussed. As an example, these methods, along with occurrence probability model of earthquake with different intensities based on the Poisson distribution, are used in analysis of seismic risk in Nanjing City. then a fuzzy conclusion is presented as a reference for decision making about earthquake resistance and protectionpolicy.