This paper discribes the manufacture of injection mold plastic magnetic gears. The pole of the right tooth face is difficult to that of the left tooth face in one teeth. Those gears mesh with the non-backlash. This paper is primarily to study the principles of plastic magnetic gears regarding the method of injection, mold method of magnetization and measurement of flux density and the results of a dynamic test (the noise test, wear test and measurement of temperature of plastic gears teeth) Regarding preventive gear noise, plastic magnetic gears are superior according to the results of the experiment. Those gears are used with no need for lubrication, but there is some degree of wear when a grease and oil lubrication is used. The shrink fit plastic magnetic gears were made as a non-lubricating type. Those types showed a slight degree of wear. The manufacture of plastic magnetic gears and polyamid coating plastic non-lubricating type. Those types showed a slight degree of wear. The manufacture of plastic magnetic gears (less than module:2) with the establishment of a new method for magnetic york. It was possible to provide a strong magnetic field by improving the magnetic york and this providing practical non-backlash gears.