Abstract: A new way of computing accurate correlation peak to increase accuracy of time-delay estimation is studied. A barrier affection caused by standard FFT calculation is reduced by calculating signal's fine spectrum with a modified Chirp z transform. A new fast algorithm of the transform FICP (Fine Interpolation of Correlation Peak) was created to compute waveform of the main correlation peak only using the main segment of the cross power spectrum. The peak can be interpolated in any accuracy without increasing calculation. The accuracy of TDE(Time-Delay Estimation) has been increased. With this way and model, interference coursed by broadband band noise can be reduced by using limited spectrum of the signal. The correlation peak will be detected precisely.