In this study we proposed a finishing tool where a slurry composited of magnetorheological (MR) fluid and abrasive particle was utilized as the polishing medium such that the rheological property and corresponding abrasive property could be controlled by changing the magnetic field. The MR abrasive fluid is magnetized by a permanent magnet. With a design of a steel C-shape structure (C-Structure) the magnetic field generated by the magnet can be directed to the tool tip. With a movable slider as a gate of the C-Structure the magnetic field directed to the tip can be adjusted continuously. The slurry was supplied from the tail and reached the tip through a fluid channel in the center of the tool. While the tool rotates with its tip near a workpiece filled with the magnetized slurry, the finishing machining process can be achieved. The usage of this finishing tool was designed to be similar as a conventional milling cutter’s tool allowing for handling surfaces of complex 3D geometries.