To　solve　the　problem　of　privacy　preservation　while　maintaining　a　high　degree　of　data　sharing　in　applications,　a　user-centric　privacy　preservation　model　is　proposed.　In　the　model,　users　are　allowed　to　set　their　privacy　through　selecting　key　words　and　special　characteristics　and　a　trust　based　method　is　used　to　determine　how　much　privacy　entropy　that　the　data　sharing　entities　can　get.　If　the　privacy　entropy　is　out　of　the　range　that　the　data　sharing　entities　can　afford,　a　substitution　method　is　used　to　help　preserve　privacy.　Simulation　results　show　that　the　method　proposed　can　protect　privacy　more　effectively　than　methods　based　on　access　control　while　offering　a　higher　degree　of　data　sharing.