Ｏｂｊｅｃｔｉｖｅ　To investigate the effect of dexmedetomidine (Dex) on epidural analgesia with morphine after cesarean section.　Methods　This is a preliminary study by a randomized, double-blind and placebo-controlled method. Eighty puerperants between 20-40 years old scheduled for cesarean section by combined spinal-epidural analgesia were randomly divided into Dex+morphine group (group A) and morphine group (group B) (n=40). Puerperants in two groups were given a single epidural injection of morphine 2.5 mg. Puerperants in group A were given continuous intravenous drip of Dex for 15 min at the dose of 0.5 μg/kg after the fetuses were taken out, then postoperative patient-controlled analgesia(PCA) at the dose of 0.1 μg·kg-1·h-1 was used. Puerperants in group B were given equal doses of physiological saline. Cortisol, renin and potassium ion concentrations in serum at the time of before anesthesia, after the operation and 24 h (T4) after the operation. Visual Analogue Scale (VAS), Observers Assessment of Alertness/Sedation Scale (OAA/S) and adverse effects during the anesthesia [4 h (T1), 8 h (T2), 12 h (T3), T4 after the operation] were observed and recorded. The urine volume(during the operation and T4) were observed and recorded.　Results　At the end of operation and T4, the averaged cortisol concentration of the puerperants in group A was lower than the concentration of patients in group B [(0.32±0.08) mg/L vs(0.36±0.08) mg/L, (0.20±0.07) mg/L vs(0.24±0.08) mg/L, P<0.05]. At the end of the operation, the averaged renin concentration of group A was lower than the concentration of group B [(30±11) ng/L vs(36±13) ng/L, P<0.05]. The potassium ion concentration was not statistically different between two groups (P>0.05). At T3, T4, the VAS of group A was lower than group B [(2.0±0.7) vs (2.3±0.6), (2.1±0.6) vs (2.4±0.7), P<0.05]. Compared with group B, the incidences of chill, nausea and vomiting were lower in group A (0 vs 6, 1 vs 7, P<0.05).　Conclusions　Continuous intravenous pumping of Dex combined with morphine in epidurale in cesarean sections can decrease stress response, adverse effects of puerpera and satisfied analgesia effects.