The present paper reviewed our recent research on illicit drugs detection by using terahertz (THz) spectroscopy technique. First, we found a THz spectral database which contains 38 types of pure illicit drugs. Second, we employ the artificial neural network (ANN) and support vector machine (SVM) methods as useful automatic tools to identify the illicit drugs. Third, a theoretical and experimental method has been developed to confirm the illicit drug purity and effective component content. Forth, Gaussian Software was used for spectral analysis of some individual samples, such as MA, ketamine, heroin, etc. Fifth, we built a smart portable Terahertz time domain spectroscopy system (THz-TDS). These works provide a solid scientific foundation for illicit drug identification by using THz spectroscopy technique. And also, as a complement detection approach, it will serve public security work.