The accuracy of the frequency estimation technique of sinusoid based on the interpolated FFT is investigated.Formulas for evaluating the root-mean-square (RMS) error of frequency estimation for different signal-to-noise ratio and different FFT length without weighting window and with Hanning window are derived.Study results show that when the frequency of the signal is close to the center of the main lobe of the FFT

due to the inversion of the interpolation direction

the interpolated FFT without weighting window results in large errors in frequency estimation.Therefore in noise background

the frequency estimation error of the interpolated FFT method is much larger than that achieved by Jain in [2] using a given pure test sinusoid signal.The effect of the weighting window on frequency estimation accuracy is also discussed.Computer Monte Carlo simulation results fit well with the formulas given in this paper.