To solve the increasingly harmonic problem which is serious and complex, this paper presented a harmonic detection method based on Kalman filter. In this paper, the Kalman filter estimation theory was discussed, and the numerical model based on Kalman filter analysis was established. Combined with the performance of the simulation platform of Matlab, it discussed the performance of the algorithm for detecting the steady harmonic and transient harmonic signal. The comparative study shows that this algorithm is superior in accuracy, rapidity, transient harmonic analysis to the Fast Fourier Transform algorithm (FFT). The simulation and experiment results show that the algorithm is quite practical in complex electric power quality analysis.