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Sum frequency generation(SFG)spectroscopy is an ideal tool to study the surface/interface,due to the surface/interface selectivity and high detection sensitivity[1].In broadband SFG(BB-SFG),an infrared pulse(IR at ωIR)and a visible pulse(VIS at ωVIS)are temporally and spatially overlapped on the sample and create the signal at ωVIS + ωIR.However the line shape of the BB-SFG spectrum is very complicated and regular spectral fitting method is hard to provide accurate information in complicated system.Frequency domain nonlinear regression(FDNLR)was proposed to retrieve vibrational properties from time-resolved BB-SFG without preset modeling of the targeted system and input laser pulses.The validity and reliability were tested by the analysis of the experimental SFG spectra(1-octandecanethiol self-assembled monolayer on gold surface).The dephasing time constants of the resonant SFG bands from the retrieved first oder polorization P(1)are consistent with the measured values.These results proved that the FDNLR algorithm is capable to retrieve the properties of the resonant vibrational SFG bands and the input pulses with improved frequency resolution.