A new electro-magnetic actuator (EMA) was designed. The newly designed EMA worked with the magnetic exclude force between the permanent magnet and electro-magnetic solenoid. And it had the advantages of single balance point, good linearity, narrow loop hysteresis, etc. The reversion of exclude force and suction force between the same magnetic pole of permanent magnet and electro-magnetic solenoid was discussed and the corresponding solution was given. The characteristic test shows that the new EMA performs good linear relation between the force and current, has a very narrow loop hysteresis and monotony and smooth relation curves between the force and displacement. Moreover, an experiment on the single-cylinder diesel also shows that even with the control of constant current only, the exclude force based on EMA can work perfectly and has a better performance than traditional EMA which works with magnetic suction force.