The incidence of delirium in the critically ill patients is high. Delirium could increase the incidence of complications and mortality in critically ill patients. Dexmedetomidine is a relative new agent used in intensive care unit (ICU), which has sedative and analgesic properties. Clinical trials have approved its advantages on prevention and control of delirium in ICU. This article reviewed the pharmacology, pharmacokinetics and application of dexmedetomidine in prevention and control of delirium in ICU.