Objective To study the vibration frequencies and resonant peaks of different molecular groups in anti-diabetic drugs and to investigate the absorption spectra of these drugs in the range of terahertz, so as to accurately and efficiently identify similar drugs and provide foundation for understanding the contribution of such vibration in different molecular groups to pharmacology. Methods Using terahertz time domain spectroscopy (THz-TDS), six kinds of similar diabetes pills for treating diabetes mellitus (DM), including gliquidone, glipizide, gliclazide, glimepiride, repaglinide and metformin were tested to obtain their absorption spectra from 0.3~3.0 THz. Support vector machines (SVM) method was employed to separate these anti-diabetic drugs by selecting the experimental data from 1.5~2.0 THz. Results For gliquidone, glipizide, gliclazide, and glimepiride, an obvious resonance peak was found at 1.37 THz. According to the THz spectra, repaglinide and metformin could be easily separated from sulfonylurea drugs. Furthermore, with the help of SVM, the accuracy of discrimination for four kinds of sulfonylurea could reach 100%. Conclusions THz technology, as a new testing method, shall play a positive role in the drugs for their identification, quality control and distinguishing their chemical bonds/functional group.