At present, more than ten monitoring indexes have been used to reflect the depth of anesthesia, from the initial bispectral index (BIS) to a variety of other indexes, such as index of consciousness, depth of anesthesia index, entropy index, auditory evoked potential, phase lag entropy and so on. However, due to the different algorithms of these indexes, each has its characteristics. This review will focus on the general principles of these monitoring indexes, their accuracy in monitoring different anesthetic sedation depths, their anti‑interference factors, and their immediacy in reflecting changes in the state of consciousness regarding BIS to provide a reference for their application in clinical anesthesia.