The model of motorized spindle was built using three dimensional software Solidworks,the velocity distribution was researched when lubricating fluid flows through the motorized spindle at different speeds,and the effect of the spindle speed and the gap between the stator and rotor of motorized spindle on the lubrication flow field was analyzed.The results show that,along with the spindle speed increasing,the lubricating fluid flow speed is increased,when the spindle speed exceeds a certain value,the lubrication fluid flow field changes dramatically and the area of maximum speed of outlet flow is generally 90 angle distribution.When fluid flows through the rotor stator gap,the velocity field in the axial direction shows first increase then decrease trend,and it presents decrease trend from the rotor surface to the stator surface in the radial direction.Increasing the length of the outlet can increase the critical speed of reflux phenomenon.