The　accuracy　design　is　an　effective　method　to　improve　machining　accuracy　of　machine　tools.　How　to　identify　key　geometric　errors　accurately　and　assign　weights　to　each　geometric　error　are　the　prerequisites　for　achieving　accuracy　design.　Therefore,　a　sensitivity　analysis　method　for　identifying　the　key　geometric　errors　is　proposed.　Firstly,　the　machining　error　model　of　machine　tools　based　on　the　multi-body　system　theory　is　formulated.　And　the　sensitivity　analysis　model　based　on　the　machining　error　model　of　machine　tools　is　established.　Meanwhile,　a　new　sensitivity　index　is　defined.　Then,　the　10th,　17th,　22nd,　24th　and　37th　geometric　errors　are　determined　as　the　key　geometrical　errors　of　the　machine　tool　by　simulation　analysis.　Meanwhile,　the　weight　of　each　geometric　error　is　allocated.　Finally,　the　＇S＇　shape　test　piece　is　selected　as　the　research　object　for　experiment　verification.　The　＇S＇　shaped　test　pieces　are　machined　by　compensating　the　identified　key　geometric　errors　and　all　geometric　errors.　And　the　formerrors　of　the　＇S＇　shape　test　piece　are　compared.　The　comparison　results　show　that　the　difference　of　the　average　profile　error　obtained　by　two　compensation　strategies　on　three　detection　lines　is　very　small,　which　is　0.　005,　0.　004,　and　0.　006　mm,　respectively.　Therefore,　the　correctness　of　sensitivity　analysis　method　is　verified.　©　2022　Science　Press.　All　rights　reserved.