The utility model relates to an excitation system controlling means, including field regulator, field regulator signal input part is connected with communication input module output through the switch, generator outlet switch branch position signal and control make the excitation move back and make two signals new auxiliary relay of adding respectively, input to digital input module and field regulator contact and communication module simultaneous working firmly, the reserve input regulator of two covers through auxiliary relay normally open contact. The utility model discloses excitation system controlling means, simple structure changes excitation transmission signal into hardwire by the communication module transmission and uses the mode with communication module, extension excitation system controlling means's life ensures the unit safety steady operation.