Presents the design of a micro boring servo system. A piezoelectric actuator is employed to compensate the deflection errors of the cutter in the radial direction to reduce the force induced errors in the workpiece. In order to bore small and deep holes, the boring bar is designed with a new structure consisting of two concentric bars, one being used for error measuring and the other for error compensation. As a result, the size of the micro boring bar is not affected even after the piezoelectric actuator and strain gauges have been incorporated. The outer diameter of the boring bar used is 16 mm and the length to diameter ratio is greater than 9. A Forecasting Compensatory Control (FCC) technique is adopted in this system for error prediction and error compensation. The off line forecasting compensatory control simulation and on line cutting results have verified that the roundness form errors in the workpiece can be reduced up to 60 percent with the developed micro boring servo system.