Abstract: A new SCR (silicon controlled rectifier) controller characterized by comprising input circuits, SCR trigger circuits, charge circuits, commutation capacitor, discharge circuits and SCR and being constructed in such way that when the input pulse is positive, it will work to activate the trigger and cause the SCR to be in turn-on state as well as to charge the commutation capacitor and when the input pulse is zero, the stored energy of the commutation capacitor will discharge to cause the SCR to be in turn-off state so that it does not need any other electric energy to attain the objective to cut off the source.