A　multi-level　and　fine-grained　access　control　method　was　presented　herein　for　CAD　models　to　meet　the　complexity　of　collaborative　design　environments　and　particularity　of　collaborative　design　process.　This　method　realized　life　cycle　protection　for　CAD　models.　Based　on　role-based　access　control　(RBAC)　and　multi-level　models,　a　multi-level　security　access　control　was　developed　to　provide　fine-grained　access　control.　Multi-resolution　models　were　created　based　on　feature　removal,　tessellations　and　mesh　simplification.　Different　resolution　models　included　different　levels　of　detail　to　those　who　have　appropriate　access　privileges,　so　the　sensitive　information　can　be　protected.　The　key　issues　of　control　client　software　features　were　discussed,　and　they　were　insurance　against　information　leak　out.　Transparent　encryption　technique　was　present　to　lift　cycle　protect　the　models　in　collaborative　environment.　A　prototype　system　was　developed　and　the　results　were　reported.　Based　on　practices,　these　methods　can　protection　the　information　of　CAD　models　effectively　during　collaborative　design.