Abstract: In the basis of analysing the leakage error caused by the finite signal duration in the spectral estimation with discrete Fourier transform, a practical approach to the leakage correction of frequency and amplitude with tonal signal components, when the power spectrum estimation is made by a FFT spectrum analyzer, is presented in this paper. One of the two window functions to be used is rectangular, the another is the Hanning window. After correction, the estimates of signal amplitude and frequency have high accuracy.