Metronidazole, tinidazole and ornidazole are 5-nitro-imidazole medicines used particularly for anaerobic bacteria and protozoa infections. The present paper reports that terahertz time-domain spectroscopy (THz-TDS) and Fourier transform infrared spectroscopy (Far-FTIR) were used to measure the fingerprint spectra of metronidazole, tinidazole and ornidazole in the frequency range of 0.9~19.5 THz under the room temperature. In addition, THz-TDS was also used to measure the absorption spectra of pure tinidazole and tinidazole tablets from different manufactures between 0.2 and 2.2 THz. In parallel with the experimental study, the cross correlation analysis was applied to compare the array of correlation coefficients between pure tinidazole and different tinidazole tablets. Results show that the method is rapid, simple and accurate to identify their effective chemical compositions and stability when the FTIR and THz spectra data combine with the array of correlation coefficient. Our research provides a visual approach to the standardization and modernization of the quality control in the production and sale of such drugs.