The indexing accuracy quasi-stopping accuracy of the electric spindle system of the turning milling compound machine tool are an important index to evaluate the spindle accuracy of the machine tool, are important factors affecting the machining accuracy of the machine tool. In order to achieve high indexing accuracy quasi-stopping accuracy of the electric spindle system, the international CNC turning milling complex machining center adopts the built-in spindle motor (referred to as the electric spindle), the spindle the motor rotor are assembled into one, reducing the influence of the intermediate transmission link on the spindle accuracy. When working, the motor rotor rotation that drives the spindle rotation. The speed ring position ring of the spindle rotation adopt high-precision feedback elements to achieve full closed-loop control, the position signal collected by the feedback elements is processed by the CNC system in frequency division, so that the resolution of the spindle indexing reaches 0.001°(the minimum indexing unit of the spindle is 3.6 ") smaller, so that the machine tool spindle system has a high indexing accuracy quasi-stopping accuracy. The turning milling compound electric spindle produced by Suzhou Deneng Motor Company can solve this problem well.