Taking　certain　CNC　camshaft　grinder　as　the　subject,　its　motion　error　analysis　and　modeling　were　studied.　The　movement　forms　and　types　of　errors　between　the　moving　parts　were　analysed,　the　movement　between　coordinate　systems　of　the　adjacent　bodies　was　used　to　express　the　movement　between　the　two　adjacent　bodies,　and　the　ideal　motion　equation　and　actual　motion　equation　in　case　of　errors　between　the　adjacent　bodies　were　set　up.　Actual　motion　equation　between　adjacent　bodies　was　made　and　further　extended　to　analyse　arbitrary　low-order　body　arrays,　which　provides　a　theoretical　basis　for　studying　the　multi-branch　CNC　camshaft　grinding　machine　error　modeling.　Complex　multi-branch　chain　CNC　camshaft　grinder　simplified　was　made　as　a　simple　multibody　system,　and　corresponding　body　coordinate　systems　and　motion　reference　coordinate　systems　for　moving　parts　were　established　to　calculate　the　corresponding　transformation　matrix　between　adjacent　bodies.　Moving　parts　of　the　machine　were　divided　into　＂workpieces-bed＂　and　＂wheel-bed＂　two　kinematic　chains.　The　precision　constraint　equation　of　the　machine　is　P-t　=　P-w　in　case　of　using　errors　influence,　and　the　constraint　equation　was　solved.　It　provides　necessary　conditions　for　study　of　CNC　camshaft　grinder　error　compensation.　Results　show　that　the　machine　precision　is　significantly　improved　after　error　compensation.