The invention relates to a single-point measurement power grid main-harmonic-source locating method based on apparent power. The single-point measurement power grid main-harmonic-source locating method based on apparent power is characterized by comprising the steps of: (1), acquiring harmonic voltage and harmonic current at a point of common coupling; (2), establishing an equivalent model of a power grid circuit, and calculating harmonic voltage and harmonic current at the point of common coupling; (3), constructing a wavelet basis function; (4), decomposing voltage and current signals at thepoint of common coupling by using wavelet transformation, and determining multi-scale decomposition coefficients of harmonic voltage and harmonic current; (5), calculating a model maximum in multiplescales by utilizing wavelet transformation; (6), performing signal and noise judgement according to a Lipschitz exponent, and detecting and improving the signal to noise ratio by the signal singularity, so that the voltage and current distortion calculation accurate can be optimized; (7), calculating the total voltage and current distortion; (8), calculating the total harmonic apparent power distortion; and (9), according to the normalized total harmonic apparent power distortion, locating a main harmonic source, and providing basis for duty allocation.