In recent years, terahertz spectroscopy has shown great potential in the fields of safety inspection, biomedicine, food detection, and resource detection. Among them, the detection of pesticide residues in agricultural products is one of the current research hotspots. This paper systematically expounds the latest research progress of terahertz spectroscopy in the field of pesticide detection, and combs the terahertz spectroscopy experimental instrument and theoretical calculation method. From the identification of pesticides, the establishment of pesticide fingerprint database, the quantitative and qualitative analysis of pesticides and the theoretical calculation of pesticides, this paper summarizes the research results obtained by scholars at home and abroad in recent years, and analyzes the existing problems and future research directions, which also provides prospects for the application of terahertz spectroscopy in the field of pesticide detection.