Regional vulnerability evaluation and zoning is a very complex process, which involves a lot of factors. And the methods of evaluation and zoning are various. Regional economic development and frequent disasters are incompatible in some ways, and extension method is an effective tool to solve incompatible problems. So this essay probes application of extension method to regional vulnerability evaluation and zoning. First, the theory of extension method and steps of application of extension method to regional vulnerability evaluation and zoning are introduced,which includes selection of indexes, defining definition field and classical field of indexes, assignments of weight among the indexes, the first evaluation, calculation of single index correlative degree and synthetical correlative degree, and zoning according to synthetical correlative degree. Factor analysis is used to calculate the weight of indexes: factor analysis of the indexes is carried in SPSS and get the commonality of each index, then deal with the commonality with the formula: where ω is the weight of each index, E_i is the commonality of each index. Since the commonality means how much the index can stand for the factors, it is reasonable to assign the weight among indexes using this method. It is proved that economic vulnerability degree contributes the most to synthetical vulnerability degree, social vulnerability degree is the next, and ecological vulnerability degree means the least. Second, Sichuan Province is taken as an example to test its effect of the application,results show that the area with highest and higher synthetical vulnerability degree takes up 85.88%, from which we can get the conclusion that vulnerability degree of Sichuan Province is high as a whole; in addition, synthetical correlative degree and single index correlative degree show that synthetical vulnerability degree and key restrictive factors differentiate a lot among regions, which means different measures should be taken according to different key restrictive factors.Zoning results show that Chengdu, Panzhihua and Deyang belong to the most slight degree, Zigong belongs to slight degree, Mianyang, Neijiang, Guang'an and Meishan belong to middle degree, Luzhou, Suining, Leshan, Nanchong, Yibing, Dazhou, Bazhong and Ziyang belong to severe degree, Guangyuan, Ya'an, Aba, Ganzi and Liangshan belong to the most severe degree. Last, a conclusion is given that application of extension method to regional vulnerability evaluation is practical, but one disadvantage of this method should be pointed out that K_j(v_i) is the distance between v_i and (a_0i,b_0i), which makes it more difficult to compare the regions belong to the same degree. But with the development of calculating method of correlative degree, extension method will supply vast vistas on researches of natural border identification and natural elements zoning.