Abstract: A simple method which can measure the chirp of femtosecond laser pulses was described.Modified spectrum autointerferometric correlation(MOSAIC) uses spectral filtering of the interferometric autocorrelation(IAC) to render a waveform that is highly sensitive to chirp.The Gaussian intensity of femto-second chirped pulses was numerically calculated.The peak of the MOSAIC minima envelope as a function of the normalized mean chirp for different orders of chirp and MOSAIC peak number corresponding to the first-and second-order chirps were obtained.Low chirp of femto-second laser pulses can be determined accurately with the MOSAIC.