A special grinding device is designed to solve the problems of the shape precision, surface quality and grinding efficiency. The device is based on the sine generator and triaxial speed to achieve the ideal Grinding trajectory. The accuracy of grinding in spherical valve core & surface quality is assured and improved by three-dimensional elastic support, pressurized floating contact and auto centering device in core and lapping tools. The grinding efficiency is highly enhanced by using the lateral and vertical speeding workpiece installration and the automatic control. The device is worth widely being applied to achieve a good large diameter hemispherical workpiece grinding.