In　order　to　achieve　a　thorough　understanding　of　the　stiffness　characteristics　of　the　Exechon　parallel　kinematic　machine　(PKM),　an　analytical　kinetostatic　model　is　proposed　by　using　the　substructure　synthesis　technique.　The　whole　system　is　decomposed　into　a　moving　platform　subsystem,　three　limb　subsystems　and　a　fixed　base　subsystem,　which　are　connected　to　each　other　sequentially　through　corresponding　joints.　Each　limb　body　is　modeled　as　a　spatial　beam　with　rectangular　cross-section　constrained　by　two　sets　of　lumped　springs.　The　equilibrium　equation　of　each　individual　limb　assemblage　is　derived　through　finite　element　formulation　and　combined　with　that　of　the　moving　platform　derived　with　Newtonian　method　to　establish　the　governing　kinetostatic　equations　of　the　system　after　introducing　the　deformation　compatibility　conditions　between　the　moving　platform　and　the　limbs.　The　computation　for　the　stiffness　of　the　Exechon　PKM　at　a　typical　configuration　as　well　as　throughout　the　workspace　is　carried　out.　Deformation　of　the　Exechon　PKM　under　an　external　load　is　computed　by　ANSYS　Workbench,　based　on　which　calculation　errors　between　the　finite　element　method　and　the　proposed　analytical　method　are　obtained　to　illustrate　the　high　accuracy　of　the　analytical　model.　The　numerical　simulations　reveal　a　strong　position-dependency　of　the　PKM＇s　stiffness,　which　is　symmetric　about　x　axis　in　a　work　plane　due　to　structural　features.　It　is　worthy　mentioning　that　the　proposed　methodology　of　stiffness　modeling　in　this　paper　can　also　be　applied　to　other　overconstrained　PKMs　and　can　evaluate　the　global　rigidity　over　workplace　efficiently　with　minor　revisions.　©　2016　Journal　of　Mechanical　Engineering.