For　assessing　the　vulnerability　of　computer　network　accurately　and　comprehensively,　the　problem　of　attack　loops,　the　state　explosion　and　analyzing　qualitatively　were　researched.　The　method　of　converting　attribute　attack　graph　to　the　Bayesian　network　and　the　new　loop　elimination　algorithm　was　also　proposed.　By　using　these　two　algorithms,　a　new　Bayesian　attribute　attack　graph　model　was　build.　The　formula　of　assessing　indicators　was　derived　by　Bayesian　formula.　The　data　of　common　vulnerability　scoring　system　was　used　to　compute　the　probability　of　attribute　nodes　and　indicators　to　conduct　network　vulnerability　assessment.　Experiments　analysis　proves　the　feasibility　and　effectiveness　of　the　model.　Compared　with　other　methods　of　vulnerability　assessment,　this　model　has　simple　calculation　which　is　suitable　for　dynamic　quantitative　assessment.　©　2015,　Beijing　University　of　Posts　and　Telecommunications.　All　right　reserved.