This paper adopts terahertz time-domain spectroscopy to identify dibutyl phthalate(DBP), one kind of industrial plasticizer. Terahertz time-domain spectroscopy techniques are used to obtain time-domain spectroscopy(0.2～1.5 THz) of different DBP concentrations in ethyl alcohol and n-hexane at room temperature in nitrogen atmosphere. Optical parameters calculation results show that refractive index, absorption coefficient and other optical parameters in 0.2～1.5 THz band of DBP/n-hexane and DBP/Ethyl alcohol solutions correspond with concentrations. According to the absorption coefficient, refractive index and correlations between frequency-domain spectroscopy of area and concentration, it can be obtained content of DBP in any unknown solutions. The results could help to provide a new way and new method to identify phthalate acid esters (PAEs) in white spirit or other soft drinks.