Nanoparticle colloid hydrodynamic cavitation jet polishing (HCJP) is a supersmooth surface machining technology that utilizes the interface reaction to remove material from workpiece, applying the cavitation effect to improve the processing efficiency. In this paper, a plototype equipment of HCJP is introduced and the experiment of HCJP and common jet polishing has been done. The experiment results indicate that in both cases, the processed area presents the orbicular structure of “W” shape when the angle of jet and horizon is 90°; the position that has the best surface quality located on the annulus of processing region where the most material removed. Compared with the common jet polishing, the surface quality processed by HCJP that uses the swirling jet is better. In processing experiment of HCJP, the supersmooth surface with roughness of Ra 0.758nm is obtained.