In order to accurately detect the parameters of harmonics in the power system, an algorithm based on a method of spatial spectrum estimation named Toeplitz was proposed on the basis of the essential property of noise information. First, eigen-value decomposition was used for the autocorrelation of matrix constructed by sampling data to get signal sub-space and noise sub-space. It adopts the principle of least squares method and rotational invariance techniques to calculate high precision signal parameter flicker .Finally, based on the estimated frequency of every signal component and the characteristic of zero average value of noise signals, the simulation results and the real-time data analysis have verified the effectiveness of the algorithm，which satisfies the needs of practical application.