The　machining　accuracy　reliability　of　machine　tools　has　important　practical　significance　for　the　quality　of　processed　parts.　In　the　milling　process,　the　geometric　errors　and　vibration　errors　are　the　two　key　error　sources　which　severely　decrease　the　machining　accuracy　reliability　of　machine　tools.　To　ensure　that　machine　tools　can　maintain　high　machining　accuracy　and　reliability　for　a　long　time,　the　paper　proposes　a　machining　accuracy　reliability　evaluation　method　that　considers　both　the　geometric　and　vibration　errors.　Based　on　the　milling　dynamics　theory　and　the　full-discretization　method　(FDM),　a　four　degrees　of　freedom　(DOF)　milling　dynamics　model　of　the　tool-workpiece　vibration　system　and　a　vibration　error　prediction　model　of　the　tool-workpiece　system　are　established.　The　former　is　used　for　the　milling　stability　prediction　and　the　milling　parameter　optimization,　while　the　latter　is　used　for　the　vibration　errors　prediction.　Utilizing　the　multi-body　system　(MBS)　theory,　a　comprehensive　error　model　considering　both　the　geometric　and　vibration　errors　is　established　to　explain　the　influence　of　errors　on　machining　accuracy.　Based　on　the　Monte　Carlo　simulation　of　directional　importance　sampling　(DIS-MCS),　a　machining　accuracy　reliability　model　is　proposed　to　evaluate　the　machining　ability　of　machine　tools.　The　method　is　applied　to　a　five-axis　CNC　machine　tool,　and　the　application　results　explain　the　correctness　and　competitiveness　of　the　proposed　method.　It　can　realize　the　milling　parameter　optimization,　the　vibration　error　prediction　of　the　tool-workpiece　system,　and　the　machining　accuracy　reliability　evaluation　of　machine　tools.