Abstract: Hair as a special biological specimen that is easy to collect, plays an important role in the field of in vivo drug analysis. The characteristics of hair and the methods for detecting illicit drugs in hair were elaborated upon in detail, and the factors influencing the detection of illicit drugs in hair were also analyzed. The prospects on the development of reference materials for detecting illicit drugs in hair and the expansion of the analytical scope in hair were proposed, aiming to provide new research ideas for the future detection of illicit drugs in hair (48 ref. cited).