The　discretionary　access　control　and　mandatory　access　control　are　two　main　access　control　modes　which　are　broadly　used　in　secure　operating　systems.　Discretionary　access　control　is　based　on　user　identity　and/or　groups　and　mandatory　access　control　is　usually　based　on　sensitivity　labels.　Neither　of　these　two　modes　can　completely　satisfy　the　requirements　of　all　access　control.　Discretionary　access　control　is　too　loose　to　restrict　the　propagation　of　privileges　while　mandatory　access　control　is　too　rigid　to　use　flexibly.　Researchers　usually　combine　two　modes　by　confining　discretionary　access　control　in　mandatory　access　control　scope　such　as　bell-lapadula　model.　This　brings　low　flexibility　of　access　control.　This　paper　discusses　some　examples　which　can＇t　be　handled　by　traditional　mandatory　access　control　based　on　bell-lapadula　model　and　proposes　a　new　method　to　integrate　the　flexibility　of　discretionary　access　control　with　security　of　mandatory　access　control　Meanwhile,　an　exception　is　defined　to　enhance　the　flexibility　of　the　model.　The　security　of　the　model　is　analyzed　and　compared　with　other　relative　works.