On the base of absorption spectra in the range of 0.2～2 THz of nine illicit drugs and three mixed drugs obtained by using terahertz time-domain spectroscopy (THz-TDS) technique, the THz absorption spectra of different illicit drugs and mixed drugs were identified by support vector machines (SVM). Absorption spectra of the nine illicit drugs and flour, which were pretreated by normalized unit, were used to train libsvm program. Absorption spectra of the illicit drugs and the mixed drugs which were measured at different time and pretreated by normalized unit too, were identified by the libsvm and the identification rate was 100%. The results indicate that it is feasible to apply SVM to identification of illicit drugs, which provides an effective method in the secure inspection and identification for illicit drugs.