With the help of the finite element analysis(FEA)software ANSYS，three dimensional model of the ultra high speed micro cutting aerostatic motorized spindle based on different support structures was set up.Finite element analysis method of fluid structure interaction was applied for the analysis of different kinds of structural designs of spindle.The load bearing characteristics was analyzed and compared in order to obtain optimized support structure of motorized spindle.It is found that the front bearing structure has the greatest effect in the bearing ability of the motorized spindle bearing,the setting of spindle span contributes a little to the bearing ability,in order to strengthen the spindle rigidity,the spindle supporting structure of front bearing with multi hole can be choosen.