The　geometric　errors　of　rotary　axes　are　crucial　error　sources　of　a　five-axis　machine　tool.　They　directly　affect　the　machining　accuracy,　and　therefore　become　one　of　the　most　important　items　for　accuracy　design.　In　this　paper,　a　prediction　and　identification　method　for　the　geometric　errors　of　rotary　axes　on　a　five-axis　machine　tool　is　proposed.　The　prediction　is　realized　by　calculating　the　mapping　relationship　between　tolerances　and　geometric　errors　of　rotary　axes,　which　is　based　on　exploring　rotary　axes＇　motion　regulation　and　Fourier　series　fitting.　Then　in　order　to　figure　out　the　practical　geometric　errors　of　rotary　axes,　the　identifying　model　is　established　based　on　homogeneous　transform　matrix　(HTM).　Double　ball-bar　(DBB)　is　adopted　to　test　error　motions　of　rotary　axes.　Finally,　a　demonstration　experiment　has　been　conducted　for　verifying　the　effectiveness　and　precision　of　the　proposed　prediction　model.　The　experimental　results　show　that　the　predicting　model　is　able　to　reflect　the　motion　principle　of　rotary　axes＇　kinematic　errors.　The　SSE,　which　expresses　residual　sum　of　squares　between　estimated　value　and　identified　point,　of　epsilon(z)(c),delta(x)(c),epsilon(y)(c),delta(z)(c),epsilon(x)(c),　and　delta(y)(c),　are　7.7716　x　10(-11),　1.2064　x　10(-4),　2.7838　x　10(-10),　2.9639　x　10(-7),　1.8966　x　10(-10),　and　2.7838　x　10(-10),　respectively.　And　R-2,　who　represent　fitting　equation＇s　coefficient　of　determination,　of　abovementioned　geometric　errors,　are　0.8978,　0.9876,　0.9978,　0.9453,　0.9985,　and　0.9978,　respectively.　The　computing　results　show　that　two　kinds　of　curves　are　basically　coincide,　and　the　proposed　method　is　proven　to　be　feasibility.