In order to solve the excitation and position sensor installment problems for the brushless synchronous machine(BSM) used as starter/generator in the variable frequency AC power system of the civil aircraft, this paper presents a novel integrated method of AC excitation and high frequency injection for the sensorless starting control of BSM. The fixed three-phase 400Hz AC power is adopted for the three phase AC excitation of BSM in the initial starting process, where the three-phase exciter works as the rotation transformer, and the resulting 6thvoltage harmonics determined by the rotating rectifier are utilized as the high frequency voltage injected into the field-winding of main generator, then the rotor position is estimated by the high frequency voltage response signals extracted from the armature windings of main generator. The frequency-insensitive asynchronous demodulation strategy is proposed for rotor position estimation, and the initial rotor position is calibrated by the polarity of induced currents of armature windings within the establishment procedure of field excitation at standstill. Finally, the excitation effect and accuracy of the position detection algorithm for BSM is validated by the simulation results.