Hard-brittle materials can be polished by hydrodynamic suspension, which is based on the theory of sound eradiating. Owing to the high-speed rotating of the polishing tool, the polishing slurry would form dynamic pressure in the clearance between the work-piece and the tool. The dynamic pressure supplies abrasive particles the energy needed to impact on the work-piece surface, so the dynamic pressure will directly affect the machining effect. In order to obtain the steady and consistent machining quality, it’s necessary to implement the compliant control in the machining process, and adjust the dynamic pressure when needed. This paper utilizes piezoelectric ceramic micro-displacement actuating to investigate the technique that can achieve the control of micro-displacement between the polishing tool and the work-piece. It provides an effective mean for hydrodynamic slurry pressure in the hydrodynamic suspension ultra-smooth machining.