Error　compensation　is　a　common　method　to　improve　the　machining　accuracy　of　five-axis　machine　tools　(FAMTs).　Before　that,　in　order　to　identify　the　key　geometric　errors　that　affect　the　machining　accuracy,　sensitivity　analysis　(SA)　in　entire　machining　region　or　a　specified　point　is　usually　used.　However,　since　the　influence　of　geometric　errors　on　form　errors　is　different　in　each　interval,　the　result　of　SA　would　be　affected,　which　decreases　the　compensating　accuracy.　For　this　reason,　a　new　approach　for　accuracy　enhancement　of　FAMTs　based　on　quantitative　interval　sensitivity　analysis　(QISA)　is　presented　in　this　paper.　First,　based　on　multi-body　system　theory　and　homogeneous　transform　matrix,　the　volumetric　error　model　of　the　FAMT　is　established.　Then,　the　geometric　error　model　of　the　FAMT　is　formulated.　Second,　development　of　form　error　model　is　involved　in　this　paper　to　clarify　the　effect　law　of　geometric　error　on　form　error.　Moreover,　the　machining　region　of　S-shaped　test　piece　is　divided　into　five　intervals.　Then,　the　QISA　method　is　presented　to　calculate　the　sensitivity　index　of　each　geometric　error　and　identify　key　geometric　errors　at　different　intervals.　Finally,　simulations　and　experiments　are　conducted　to　validate　the　feasibility　and　effectiveness　of　the　presented　method.　(C)　2020　Elsevier　Ltd.　All　rights　reserved.