A　3-DOF　parallel　mechanism　with　large　positional　workspace　is　proposed,　which　is　a　varietal　type　of　the　Tricept　mechanism.　The　structural　characteristic　of　the　presented　mechanism　is　that　the　passive　sub-chain　of　Tricept　mechanism　is　integrated　into　one　of　its　three　active　sub-chains,　and　the　three　axes　of　active　joints　are　perpendicular　to　each　other　and　intersect　one　point.　The　positional　workspace,　kinematic　dexterity　and　stiffness　property　of　the　mechanism　are　analyzed,　The　graphic　descriptions　of　the　relationships　between　performance　changes　of　mechanism　versus　the　varieties　of　its　dimensional　parameters　are　presented.　The　analysis　shows　that　for　mechanisms　with　different　dimensional　parameter　combinations　and　smaller　limitative　angles　of　universal　and　spherical　joints,　the　movable　platforms　can　obtain　large　positional　workspaces.　In　addition,　the　mid-regions　hold　larger　proportion　of　volume　values　of　the　positional　workspaces,　and　the　movable　platforms　have　better　dexterity　and　stiffness　in　mid-regions.　The　graphic　descriptions　acquired　illuminate　the　relationships　between　kinematic　performance　and　mechanism＇s　dimensional　parameters　fully　and　can　be　applied　to　further　characteristic　analysis　and　kinematic　design　of　mechanisms.