Objective: A history of stroke is the independent risk factor for postoperative delirium. The objective of this research is mainly to explore the effects of low-dose dexmedetomidine (DEX) infusion on postoperative delirium incidence of elderly patients with a history of cerebral stroke. Method: 161 elderly patients (>=65yrs) with a history of cerebral stroke who were admitted to Intensive Care Unit after surgery were randomly assigned to receive either an infusion of low-dose DEX (0.1 μg/(kg·h) or placebo (saline). Delirium were assessed twice daily with the Confusion Assessment Method for the ICU (CAM-ICU) for 7 days after surgery. Results: The incidence of postoperative delirium was significantly lower in the DEX group than in the placebo group (DEX group 14.6% [12/82] vs placebo group 29.1% [23/79], P=0.026). Multivariate Logistic regression analysis showed that low-dose DEX infusion were independently associated with the risk of reduced postoperative delirium (OR 0.36, 95% CI 0.15-0.89, P=0.027). Hypotension occurred in 42.7% [35/82] DEX group and 24.1% [19/79] placebo group (P=0.012), however, the intervention with hypotension did not differ between the two groups. Conclusion: For the elderly patients with a history of cerebral stroke and transferred to ICU after surgery, postoperative prophylactic infusion of low-dose DEX could reduce the incidence of postoperative delirium, but the blood pressure should be monitored.