Abstract: A new real-time accurate estimating method for electric power harmonic and inter-harmonic parameters is proposed.First,the estimating algorithm of frequency and phase estimation for a harmonic or inter-harmonic is deduced using the discrete spectrum power center of symmetric windows,and then the amplitude calculation of electric power harmonic is inferred by using Parseval theorem.The estimation error is analyzed.The estimation error of an electric harmonic is only related to the energy distribution of the weighted window function in the frequency domain.The relative error of an electric harmonic is no greater than the proportion of the spectrum energy of the window function in the side lobe to the total.Finally,the simulation tests show that the method proposed has apparent advantages in computing time consumption over other windowed Fourier transform interpolation corrective analysis methods.The results of physical simulation tests show that the method proposed is very suitable for embedded systems and digital signal processors.