The　geometric　error　of　machine　axis　can　be　equivalent　to　the　differential　movement,　regarded　as　a　differential　operator　based　on　its　ideal　position.　Thus,　a　new　modeling　method　for　multi-axis　CNC　machines　based　on　differential　transform　theory　is　proposed　in　this　paper.　Firstly,　the　workpiece　coordinate　system　is　selected　to　observe　the　error　of　tool＇s　cutter　location　and　orientation.　Then,　the　kinematics　chain　of　the　machine　will　be　consolidated　into　one,　and　the　closed　chain　can　be　changed　to　open　series　type.　The　transform　matrix　is　adopted　to　convert　the　differential　operator　between　the　different　basis,　because　of　the　geometric　errors　have　a　different　basis　between　measurement　and　modeling.　Eventually,　the　general　geometric　error　model　for　multi-axis　machines　is　established　after　a　XYFZ　type　three-axis　machine　is　studied　in　detail.　©　(2012)　Trans　Tech　Publications,　Switzerland.