The invention provides a single-tube IGBT (Insulated Gate Bipolar Translator)-based three-stage brushless generator power control device and a power control method. The single-tube IGBT-based three-stage brushless generator power control device comprises a minimum system, a control circuit, a power unit, a power module, an auxiliary exciter, a main exciter, a generator, a first voltage measurement transformer, a second voltage measurement transformer, a third voltage measurement transformer, a first current transformer, a second current transformer, a Hall voltage sensor, a Hall current sensor, a given voltage circuit, an excitation relay, a deexcitation relay, an IGBT drive circuit, an analog input circuit, a phase-locked loop frequency doubling circuit, a discrete input photoelectric isolation module and a discrete output photoelectric isolation module. Because the single-tube IGBT is adopted as a power switching device, switching loss can be effectively reduced, the response speed can be effectively increased, and the reliability is high; a controller is adopted as a main control unit to accurately control the three-stage synchronous generator; because the single-tube IGBT-based three-stage brushless generator power control device can communicates with an upper computer to monitor the system, faults can be rapidly and conveniently diagnosed and overhauled.