Abstract: In order to effectively detect the SBS ( Styrene-Butadiene-Styrene Copolymer) content in modified asphalt，an improved method based onInfrared spectroscopy is presented． By comparing the SBS modifier’ sspectroscopyandmatrix asphalt's spectroscopy，the characteristic absorbance peak at 966 of SBS modifier is used to detect the SBS content． Compound Simpson formula is introduced to calculate the peak area． Then，according to Lambert-Beer's law，the standard curve of the relationship between peak area ratio and SBS content are obtained by least square method． Finally，modified asphalt with different SBS contents are prepared from 70# matrix asphalt of Liao He Petrochemical Company． The average error of calibration samples and test samples is 0． 14% and 0． 02% respectively． The results show that the proposed method has the advantages of fast speed，high precision and easy operation compared with the original methods such as GPC． It provides a scientific and effective method for timely detection of asphalt SBS content in road construction projects in the future．

Key words: styrene-butadiene-styrene ( SBS ) copolymer modifier, matrix asphalt, infrared spectroscopy, compound simpson formula, least square method