Fluid magnetic abrasive (FMA) is a new precision finishing process. It has the capability of processing free shape surfaces and complex cavities. Due to its strong adjustability and controllability, FMA could be regarded as the final process of machining which could greatly improve the surface quality of workpiece. The paper first introduces the component and machining mechanism of FMA, secondly it describes the model of the material removal in the process, thirdly it presents the devices of FMA polishing. At the end, a grinding head tool based machining mode is proposed for realizing the polishing of internal cavity.