In　order　to　satisfy　the　demand　of　on-line　automatic　balance　of　a　grinding　wheel　and　motor　spindle,　we　introduced　an　on-line　automatic　balance　system　and　designed　an　automatic　electromagnetic　balancer.　We　conducted　a　study　on　the　design　method　of　interference　fits　in　an　automatic　electromagnetic　balancer　based　on　the　finite　element　method.　The　simulation　results　demonstrated　that　the　interference　tolerance　fit　for　this　automatic　electromagnetic　balancer　was　between　4μm　and　16　μm.　We　made　automatic　electromagnetic　balancers　with　an　interference　tolerance　of　5　μm,　which　satisfied　the　demand　of　on-line　automatic　balance.　Finally,　we　conducted　experiments　to　test　the　function　of　the　automatic　electromagnetic　balancer　at　1　834　r/min.　The　experimental　results　showed　that　the　unbalance-induced　vibration　could　decrease　by　at　least　80%.　©　2017,　Editorial　Department　of　JVMD.　All　right　reserved.