A hydrodynamic suspension ultra-smooth machining system based on NC machine tool was constructed. The structure and the operating process of the hydrodynamic suspension ultra-smooth machining system were introduced. The submicroscopic cutting of work pieces conducted for surfaces of k9 optical glass, on which ultra-smooth surfaces were realized. The mechanism of hydrodynamic suspension ultra-smooth machining was analyzed. The experimental results show that the hydrodynamic suspension machining technique is available for ultra-smooth machining of optical materials.