Asphalt, SBS and SBS modified asphalt binders with six different contents of SBS were tested by Fourier transform infrared spectrophotometer(FTIR). Results indicate that the characteristic absorbance peaks at 966 cm-1 and 699 cm-1 for SBS and 810 cm-1 for asphalt could be used as the qualitative and quantitative basis for the determination of contents of SBS. One way analysis of variance and multiple comparison showed that SBS content had a significant effect on the absorption area ratio of the peaks at 699 cm-1 and 810 cm-1(A699/A810). A699/A810 ratio indicated a significant difference among SBS modified asphalt binders with different contents of SBS. So A699/A810 could be selected as quantitative indexes for SBS content since A699/A810 presents good linear relationship with SBS content(correlation coefficient was 0.9983).A rapid method determination of SBS content in SBS modified asphalt binders by FTIR is developed.