Abstract: In order to improve the grinding accuracy, the design and optimization of hydrostatic bearing of motorized spindle were studied from the point of view of motorized spindle. The hydrostatic plain bearing is designed with four oil chamber structure and orifice throttling mode. The main design parameters include throttling ratio, radius clearance, return groove width and sealing surface width. The stiffness calculation model of the small-orifice throttling hydrostatic bearing was established, and the influences of throttling ratio, radius clearance, return groove width and sealing surface width on the support stiffness of the hydrostatic bearing were analyzed. Orthogonal experiment was used to optimize the design of bearing throttling ratio, radius clearance, return groove width and sealing surface width, and the primary and secondary order of influence of the above four parameters on bearing stiffness was obtained through range analysis, so as to obtain the optimal parameter combination. The results show that when the radius clearance is 0.04 mm, the orifice throttling ratio is 1.8, the width of the oil return groove is 12 mm, and the width of the oil sealing surface is 20 mm, the bearing oil film stiffness is the maximum. The research results of this paper can provide reference for improving the precision of high precision machining machine tools.