The invention relates to a workpiece partial high-precision polishing device based on a magneto-rheological effect. The device comprises a motor, a coupling, a rotary shaft, a transparent containing box, a polishing wheel, permanent magnets, movable bearing pedestals, a polishing table, a workpiece, a polishing solution, a high-pressure nozzle, a pump and a normal force sensor. The polishing wheel is connected with the rotary shaft and driven by the motor through the coupling. The rotary shaft is suspended on the movable bearing pedestals, and the movable bearing pedestals are mounted in the transparent containing box. The polishing table is arranged in the middle of the transparent containing box, the workpiece is arranged on the polishing table, the normal force sensor is embedded in the polishing table, and the distance between the polishing wheel and the polishing face of the workpiece is 2 mm. The two permanent magnets are mounted on the polishing wheel and are arranged in a heterospolar manner, and the pump is arranged in the end angle area, opposite to the polishing direction of the workpiece surface, in the transparent containing box. The polishing solution is composed of water-based magneto-rheological fluid and a polishing grinding material. The magneto-rheological fluid is water-based magneto-rheological fluid with the iron powder mass percent being 81.83%, the iron powder diameter ranges from 2 micrometers to 8 micrometers, and the grinding material is irregular-shape AlO3 particles.