The main reason of choosing self-shunt brushless excitation System in nuclear power station is firstly introduced in this paper，and the structure & function of brushless excitation system are analyzed, the characteristic of flashing excitation and boosting excitation are emphasized, rotor one-point earthing protection and other protection for excitation circuit are analyzed, and the method of de-excitation characteristic is described, self-shunt Brushless Excitation System is suitable for high capacity unit，it will has broad application in nuclear power station.