At　present,　it　is　difficult　to　predict　the　operation　accuracy　of　machine　tools　in　the　preliminary　design　stage.　How　to　quantitatively　reflect　the　contribution　of　tolerance　on　the　position　error　of　machine　tool　has　a　significant　guidance　for　machine　tool　design　stage.　Thus,　this　paper　presents　a　sensitivity　analysis　method　based　on　components　tolerance,　which　can　clearly　give　the　machine　tool　designer　key　the　tolerances.　Firstly,　taking　the　translational　axis　as　the　research　object,　the　operation　accuracy　model　of　Y-axis　is　established　based　on　the　homogeneous　transform　matrix　(HTM)　and　multi-body　system　(MBS)　theory.　Meanwhile,　the　relationship　between　tolerances　and　geometric　errors　has　been　mapped　by　the　Fourier　expansion　and　the　model　of　parameters　have　been　identified　by　self-design　simulation.　As　a　basis,　the　tolerance　sensitivity　analysis　(TSA)　method　based　on　the　single-factor　partial　derivation　is　constructed　to　acquire　the　key　tolerance　parameters.　Finally,　the　result　of　the　experiment　shows　that　the　assembly　tolerance　of　the　Y-Z　plane　of　the　base,　the　manufacturing　tolerance　of　the　lead　screw　and　the　assembly　tolerance　of　the　X-Y　plane　of　the　carriage　contribute　a　great　deal　to　the　position　error,　which　needs　to　be　strictly　controlled　in　the　future　design　to　improve　the　accuracy　of　the　machine　tool.