Abstract: According to the site classifications and their uncertain and stochastic characteristics,the site classification method based on qualitative reasoning of 2-D & multi-rules cloud model was constructed and the uncertain division of the site classification was realized.Then,the generator on 2-D & multi-rules for uncertainty reasoning was designed to identify site classifications and site characteristic period,so the continuity of the site classification and site characteristic period were actualized.This method got rid of the illogical discontinuity and appreciable distinction displayed on the code chart between the site edges,basically realized the unification of the site classification between code of seismic design of buildings and special structures.Finally,74 examples were analyzed by the method.It was shown that the sites were classified with the correct rate of 97.3%,and the method proposed in the paper proved to be effective and feasible.