ODS　(Operating　Deflection　Shapes)　and　modal　testing　are　used　to　analyze　vibration　frequency　and　working　deformation　of　EDM　machine　tool　spindle　head　for　finding　the　weak　part　of　the　structure　and　the　target　modal　through　test　results　in　actual　conditions.　A　more　accurate　finite　element　model　of　the　spindle　head　is　obtained　by　modifying　the　original　model　based　on　the　comparison　between　analysis　result　of　the　original　model　and　the　result　of　the　real　modal　test.　The　target　modal　frequency　of　spindle　head　is　increased　by　30.93%　by　using　optimization　method,　which　utilizes　the　ISIGHT　optimization　software　to　integrate　SolidWorks　and　ANSYS　to　optimize　the　dynamics　of　the　weak　part.　The　test　and　optimization　method　presented　in　this　paper　can　be　used　to　provide　a　convenient　and　effective　way　to　improve　the　structural　dynamics　of　the　machine.