A method was proposed to quantitatively inspect the mixtures of illicit drugs with terahertz time-domain spectroscopy
technique. The mass percentages of all components in a mixture can be obtained by linear regression analysis, on the
assumption that all components in the mixture and their absorption features be known. For illicit drugs were scarce and
expensive, firstly we used common chemicals, Benzophenone, Anthraquinone, Pyridoxine hydrochloride and L-Ascorbic
acid in the experiment. Then illicit drugs and a common adulterant, methamphetamine and flour, were selected for our
experiment. Experimental results were in significant agreement with actual content, which suggested that it could be an
effective method for quantitative identification of illicit drugs.