Privacy　protection　is　one　of　the　important　topics　in　network　security.　Although　a　lot　of　work　has　been　done,　there　are　still　some　open　issues　and　challenges　that　need　to　be　addressed.　Now,　open　and　dynamic　computing　environments　offer　flexible　and　convenient　sharing　of　information　and　services　for　users.　Consequently,　there　exist　a　lot　of　different　policies　for　privacy　protection　to　deal　with　dynamic　changes　in　each　application　scenario.　This　raises　the　issue　of　privacy　policy　specification.　Although　trust　can　help　protect　user　privacy,　the　use　of　unified　trust　values　or　a　simple　trust　rank　cannot　satisfy　the　requirement　for　privacy　protection　because　different　privacy　may　need　its　own　trust　evidence　for　the　evaluation　of　trust.　To　solve　this　problem,　we　propose　a　novel　approach　for　privacy　protection　based-on　ontology　in　this　paper.　Our　main　contributions　in　this　paper　include　(1)　specifying　privacy　policies　in　a　semantic　way　and　(2)　abstracting　the　policies　as　trust　attributes　for　privacy　ontology.　In　addition,　our　method　can　be　used　to　protect　sensitive　policies　at　the　same　time.　©　2010　IEEE.