Abstract: In order to study the composition of science and technology security capability of national defense industry and evaluate the security capability of the industry's major fields, an evaluation index system was constructed from three dimensions:operation capability, promotion capability and guarantee capability. To adapt to the subjectivity of the evaluation object and the characteristics of the small sample, the weight of the evaluation index system was calculated by the Modified Combination Weighting Approach. And the security capability of the industry's six major fields was compared by using the Topsis Method. The results show that promotion capability and guarantee capability are the core of the security capability, while operation ability is the foundation; the higher development level of the industrial field, the stronger the security capability; the promotion capability is the strongest aspect, while the guarantee ability is the weakest.