Vulnerability to hazards includes not only components of a physical nature, but also those arising from social factors. In developing measures for disaster prevention or emergency response for disaster relief of big cities, an analysis of social vulnerability is very necessary but quite difficult. In order to address the problem, using Beijing as an example, we established a social vulnerability index system including 26 factors and developed an improved analytic hierarchy process (AHP) method. The weight of each factor was evaluated using the improved AHP process that obviously increased the passing rate of consistency of the experts’ questionnaire. The population, career, economy, infrastructure and social vulnerability distribution maps of Beijing were obtained. From them, it’s easy to see the characteristics of various vulnerability distributions. Through sensitivity analysis, the influencing factors of each area were listed in order of importance. The approach are useful for assessing, reducing the social vulnerability of big cities in China. Vulnerability to equals not only components of a physical nature, but also that arising from social factors. to address the problem, using Beijing as an example, we established a social vulnerability index system including 26 factors and developed an improved analytic hierarchy process (AHP) method. The weight of each factor was evaluated using the improved AHP process that obviously increased the passing The population, career, economy, infrastructure and social vulnerability distribution maps of Beijing were obtained. From them, it’s easy to see the characteristics of various vulnerability distributions. Through sensitivity analysis, the influencing factors of each area were listed in order of importance. The approach are useful for asses sing, reducing the social vulnerability of big cities in China.