The invention discloses an excitation system excitation-enabling power supply structure and a control method. The excitation system excitation-enabling power supply structure comprises an alternating-current 380V auxiliary excitation-enabling power supply wire inlet end, wherein the alternating-current 380V auxiliary excitation-enabling power supply wire inlet end is connected with an air switch QF03 wire outlet end, the air switch QF03 wire outlet end is connected with an alternating-current auxiliary excitation-enabling power rectifier wire inlet end, an alternating-current auxiliary excitation-enabling power rectifier wire outlet end is connected with a relay K03 wire inlet end, a K03 wire outlet end is connected with an excitation system inlet wire power supply wiring end, a direct-current starting excitation-enabling power supply is connected with an air switch QF04 wire inlet end, an air switch QF04 wire outlet end is connected with a resistor R04, the resistor R04 is connected with a relay K04 normally-opened contact, and the relay K04 normally-opened contact is connected with the relay K03 wire inlet end. The technical problem that a power plant set excitation system is insufficient in residual voltage under the situation that a whole power plant lose voltage when adopting residual voltage of a main transformer to enable excitation due to disappearing of auxiliary excitation-enabling alternating current, and accordingly normal starting cannot be performed is solved.