Fourier transform infrared spectrometer (FTIR) can obtain the far-infrared spectrum of the material and identify the unknown samples according to its fingerprint characteristic spectrum. In this experiment, FTIR was used to test the absorption spectra of five standard drugs, such as cocaine, ketamine hydrochloride, cannabinol, heroin and morphine, in the far-infrared band (30-350 cm^-1) under vacuum conditions, and some absorption peaks were described and analyzed. The results show that the five standard drugs have obvious characteristic absorption peaks in the far infrared band. This study provides a data basis for the establishment of far infrared spectrum database for drug identification.