The invention relates to a third-level type motor rotor position estimation method for salient pole characteristic change. Targeted to characteristics of a third-level type motor multi-level combination structure, a new signal transfer and detection channel is established between a main generator and an exciter and is shown as the graph 2; high-frequency signals are injected on the stator side of the main generator through the signal transfer channel, the signals sequentially pass through a main generator air-gap magnetic field, a rotating rectifier and an exciter air-gap magnetic field, then high-frequency response signals are extracted out of an exciter stator winding, and estimation of the position of a motor rotor is achieved. According to the main generator injection-exciter detection signal transfer and detection thought, the characteristic that mutual inductance between the main generator stator winding and the exciter winding changes along with the position of the rotor is fully utilized, and the position of the main generator exciter winding, namely the position of the rotor magnetic pole is estimated. The estimation method does not depend on salient polarity of a motor, and the method is still applicable when the main generator salient polarity changes in the starting process.