The invention discloses a power grid resonance point detection method based on a constant-voltage source converter. The method comprises the steps that first, the designed constant-voltage source converter is utilized to input carrier voltage signals with an equal amplitude and different frequencies into a low-voltage side of a transformer; second, a voltage signal U(t) and a current signal I(t) at the low-voltage side of the transformer are detected; third, according to a sliding DFT algorithm, voltage-current harmonic waveforms of the different frequencies in the measured signals are extracted; fourth, according to a Pearson correlation coefficient calculation formula, a correlation coefficient among the voltage-current harmonic waveforms of the different frequencies is calculated; and fifth, according to the calculated correlation coefficient among the voltage-current harmonic waveforms of the different frequencies, resonance points are determined. The method is easy to implement, it is only needed to operate equipment to input the low-frequency carrier voltage signals, and then the equipment can automatically detect the resonance points. Besides, through the method, the calculation amount is small, measured data does not need to be uploaded to a master station and can be analyzed locally, and therefore real-time online detection on the resonance points can be realized.