Abstract: Objective To investigate the effect of infusion of dexmedetomidine on postoperative patients with upper abdominal surgery after fentanyl for patient-controlled intravenous analgesia. Methods Seventy-four patients in our hospital were divided into observation group and control group.Postoperative patient controlled intravenous analgesia.The observation group with dexmedetomidine combined with fentanyl.The control group was only used fentanyl.After 1,6,12,24,48 hours,compared with two groups of MAP,HR,SpO₂,VAS score,Ramsay score.Compared with two groups of effective pressing times,fentanyl dose and adverse reactions. Results In the observation group,the effective pressing times and the dose of 48 h fentanyl were significantly lower than those of the control group.The difference was statistically significant (P<0.05).The observation group 1,6,12,24 hours of MAP,HR was significantly lower than the control group.The difference was statistically significant (P<0.05).There was no significant difference in SpO₂ levels between the two groups at each time point (P>0.05).After 1,6,12 and 24 hours,the VAS score of the observation group was significantly lower than that of the control group,the Ramsay score was significantly higher than that of the control group.The difference was statistically significant (P<0.05).The incidence rate of adverse reaction in the observation group (8.11%) was significantly higher than that in the control group (29.73%).The difference was statistically significant (χ²=5.638,P<0.05). Conclusion The effects of dexmedetomidine combined with fentanyl in patients undergoing upper abdominal surgery postoperative patient-controlled intravenous analgesia,and independent use than fentanyl,can achieve better analgesic and sedative effect,reduce the dose of fentanyl and the occurrence of adverse reactions,effectively.