Objective To investigate the effect of dexmedetomidine on postoperative patient-controlled intravenous analgesia (PCIA) with sufentanil in patients with essential hypertension. Methods Sixty ASA Ⅱ or Ⅲ patients with essential hypertension aged 42-63 yr weighing 48-72 kg undergoing hysterectomy were randomly divided into 3 groups ( n = 20 each): control group ( group C) and different doses of dexrmedetomidine groups ( group D1.2 ). PCIA was performed with sufentanil 1 μg/ml + tropisetron 5 μg/ml in 100 ml of normal saline within 24 h after operation (background infusion at 2 ml/h with a bolus dose of 0.5 ml and a 15 min lockout interval). Dexmein group C. Ramsay score was recorded. The number of attempts, consumption of sufentanil, the number of patients who needed nifedipine or ephedrine and side effects such as vomiting and respiratory depression were recoded within 24 h after operation. The level of sedation was evaluated with Ramsay sedation score at 24 h after operation.Results Compared with group C, the number of attempts, consumption of sufentanil, the number of patients who needed nifedipine and incidences of vomiting and respiratory depression were significantly decreased, while Ramsay score was significantly increased in D1 and D2 groups, and the number of patients who needed ephedrine was significanlly increased in group D2 ( P ＜ 0.05). The number of attempts and consumption of sufentanil were significantly decreased, and Ramsay score and the number of patients who needed ephedrine were significantly increased in group D2 compared with group D1 ( P ＜ 0.05). Conclusion Dexmedetomidine can not only reduce the consumption of sufentanil for postoperative PCIA, but also prevent postoperative hypertension from deteriorating in patients with essential hypertension.