Abstract: The spectral phase shift of broadband pulse caused by transient random disturbance was investigated,based on the combination of the characteristics of linear chirped pulse and the spectral interferometry of two pulses.When the same component of both the pulse spectra meet on the frequency domain,the spectral interference is generated.Extracting spectral phase difference between both the linear chirped pulses from the spectral interferogram,it was simulated based on Fourier transform spectral interferometry(FTSI).The results show that reconstructed phase shift of chirped pulses is characteristic of spectral change,and this reconstruction algorithm is effective.This method is helpful to transient measurement of some physical quantity in ultrafast optics.