In this paper, we are rolling in damage data and the results of a laboratory tests. A set of predictable method that is satisfactory to China's Northwestern sites damage are established with the principles of information distribution, fuzzy multifactorial evaluation and information concentration. Site is classified into three sorts:stable region, stable region in the main and non-stable region. Evaluated paramenters are geography and geomorphology, soil liquefaction potential, loess settlement, the thickness of artificial filled soil, the depth of soft soil and slope stability. The damages of a few sites of Xian and Baoji Cities are evaluated by this method. And its results are in keeping with those of macrosopic analysis. This paper provide the prediction of China's Northwestern sites damage with a kind of quantitive research method. At same time, it is of importance to research of seismic microzonation.