Abstract: Based on the spectral phase interferometry of direct electricfield reconstruction (SPIDER), the spectral phase of femtosecond laser pulse was reconstructed with numerical simulations. Several crucial parameters, such as the time delay, frequency shear, width of filter window and dispersion were analyzed on the optimal selection. When the dispersion and pulse width were given, the time delay had an optimum range. When the relative spectral shear was 5% ~15% and the width of filter window was /3 ,the reconstructed phase error was minimum. The noise was reduced by taking mean of the interferograms. The characterization of Ti:sapphire pulse was measured by using SPIDER. The comparison with autocorrelation measurement showed the validity of experiment.