Method for on-line estimation of an initial position of a surface permanent magnet electric machine in a stationary state or at a first speed, the method comprising: injecting a high-frequency pulsating voltage signal; acquiring a d-axis high-frequency current signal responding to the high-frequency pulsating voltage signal; and estimating an initial position of the surface permanent magnet electric machine on the basis of a second harmonic of the d-axis high-frequency current signal, wherein the initial position comprises a rotor salient pole position and a rotor position polarity, and wherein the step of estimating an initial position of the surface permanent magnet electric machine on the basis of a second harmonic of the d-axis high-frequency current signal further comprises: converting the d-axis high-frequency current signal to a d-q coordinate system so as to obtain a first component (i q) and a second component (i d); and subjecting the second component (id) to band-pass filtering, cosine processing, low-pass filtering and polarity determination so as to obtain a rotor position polarity of the surface permanent magnet electric machine, characterized by subjecting the first component (i q) to band-pass filtering, sine processing, low-pass filtering, and observation using a Luenberger observer or phase-locked loop circuit, so as to obtain a rotor salient pole position of the surface permanent magnet electric machine. injecting a high-frequency pulsating voltage signal; acquiring a d-axis high-frequency current signal responding to the high-frequency pulsating voltage signal; and estimating an initial position of the surface permanent magnet electric machine on the basis of a second harmonic of the d-axis high-frequency current signal, wherein the initial position comprises a rotor salient pole position and a rotor position polarity, and wherein the step of estimating an initial position of the surface permanent magnet electric machine on the basis of a second harmonic of the d-axis high-frequency current signal further comprises: converting the d-axis high-frequency current signal to a d-q coordinate system so as to obtain a first component (i q) and a second component (i d); and subjecting the second component (id) to band-pass filtering, cosine processing, low-pass filtering and polarity determination so as to obtain a rotor position polarity of the surface permanent magnet electric machine, characterized by subjecting the first component (i q) to band-pass filtering, sine processing, low-pass filtering, and observation using a Luenberger observer or phase-locked loop circuit, so as to obtain a rotor salient pole position of the surface permanent magnet electric machine. converting the d-axis high-frequency current signal to a d-q coordinate system so as to obtain a first component (i q) and a second component (i d); and subjecting the second component (id) to band-pass filtering, cosine processing, low-pass filtering and polarity determination so as to obtain a rotor position polarity of the surface permanent magnet electric machine, characterized by subjecting the first component (i q) to band-pass filtering, sine processing, low-pass filtering, and observation using a Luenberger observer or phase-locked loop circuit, so as to obtain a rotor salient pole position of the surface permanent magnet electric machine.