Abstract: Objective To investigate the effects of dexmedetomidine on the analgesic efficacy of fentanyl in patients undergoing upper abdominal surgery. Methods A total of 76 patients in Shaoxing Central Hospital between August 2014 and March 2016 were divided into FD group (n=38) and F group (n=38).All patients were operated by static suction combined with general anesthesia,and the patients were all connected with the analgesia pump for self-controlled intravenous analgesia.FD group was given 400 μg of dexmedetomidine combined with fentanyl 0.8 mg.F group was only given0.8 mg fentanyl.The self-controlled analgesia and the dosage of fentanyl between the two groups were compared.At 2,4,6,12,24,the visual analogue scale (VAS score),analgesia score (Prince-Henry score),sedation score standard (Ramsay score) between the two groups were compared.The complications (nausea,vomiting,excessive sedation,hypotension,itching,tachycardia,respiratory depression) were observed. Results FD group for the first time (77.92±15.61) min,total pressing times (29.12±9.25) times,the dosage of fentanyl (426.71±20.53) ml were significantly lower than the level of each index of F group[(54.68±13.95) min,(45.36±15.34) times,(509.54±26.12) ml].The difference was statistically significant (t=7.415,5.589,15.369,P<0.05).After the surgery,at 2,4,6,12,24,VAS score and PrinceHenry score in FD group were significantly lower than those in the F group,the difference was statistically significant (P<0.05).There was no significant difference in Ramsay scores between the two groups at different time points (P>0.05).The incidence of adverse reactions in group FD (7.89%) was significantly lower than that in group F (28.95%),and the difference was statistically significant (χ²=4.290,P<0.05). Conclusion Dexmedetomidine can significantly increase the analgesic effect of fentanyl in patients undergoing abdominal surgery,and reduce the dosage of fentanyl and adverse reactions.