Abstract: Alpha 2- adrenergic receptor agonist has sedative，anti-anxiety，hypnotic and analgesic effects. Dexmedetomidine （Dex） is a new，potent and highly selective alpha 2- adrenergic receptor agonist.The present study showed that Dex could reduce the sedative and opioid dose，stabilize hemodynamics，and had the effects on anti-inflammation and organ protection，anti-shaking and salivation as well as other pharmacological properties in a wide range of clinical applications. Dex is considered to be a safe and effective adjuvant，or in single use of therapeutic agent in clinical anesthesia，it has a broad application prospects. From the mechanism of Dex，preoperative，intraoperative nerve block and spinal anesthesia，general anesthesia and postoperative adjuvant drug use，organ protection，ICU sedation etc. This article reviews its application in clinical anesthesia，and provide a theoretical basis for the clinical application and basic research of Dex.

Key words: dexmedetomidine, action mechanism, clinical perioperative period, calm, analgesia