[Objective] The aim was to explore the application of terahertz （THz） technique in pesticide recognition and residue determination. [Method] THz far-infrared spectral characteristics of 2 herbicides （butachlor and metolachlor） were measured by THz time-domain spectroscopy （THz-TDS） under conditions of room temperature and nitrogen,meanwhile their refractive index and absorption coefficient between 0.2 and 2.2 THz were calculated by using models based on Fresenl equations. [Result] The 2 pesticides both had a series of different characteristic absorption peaks between 0.2 and 2.2 THz,respectively. Their molecular structures were similar,but there were great difference in absorption and refractive index spectrum between them. [Conclusion] THz-TDS technique is feasible to detect pesticide residues,especially there is a greater advantage in identifying the structure of similar substances.
