A　new　Role-based　Mandatory　Access　Control　(RBMAC)　model　which　combine　BLP,　BIBA　and　RBAC　models　is　proposed.　The　model　describes　hierarchical　organization　structure　as　information　categories　and　user＇s　roles,　define　most　critical　links　of　file　treatment　as　integral　classification　and　clearance.　We　also　apply　some　concepts　as　trusted　subject,　task,　invite　role　and　actor　in　order　to　satisfy　access　control　request　from　important　information　systems.　The　formal　definition,　theorem　systems　and　operation　rules　of　RBMAC　model　are　illustrated　in　this　paper.　Trusted　subject　is　responsible　for　change　confidential　classification　and　integral　classification　and　categories　in　RBMAC　model,　whose　methodology　is　same　as　actual　works.　The　experiment　shows　that　RBMAC　model　is　flexible　and　efficient.