Objective: To study the distribution characteristics of CYP3A4*1G in Xinjiang Uygur and Han nationality population, and their relationships with postoperative dosage of fentanyl and the analgesia effects. Methods: 71patients with gynecological surgery under general anesthesia were selected, who were at grade I or II according to American Society of Anesthesiologists (ASA). The patients were divided into two groups based on nationality: the Uighur nationality group (group U, n=37) and the Han nationality group (group H, n=34). Polymerase chain reaction - restriction fragment length polymorphism (PCR - RFLP) was adopted to detect the polymorphism of CYP3A4*1G. Patient controlled intravenous analgesia (PCIA) with fentanyl was adopted. And the visual analogue scale (VAS), Ramasay sedation scores and vital signs at postoperative 6, 24 and 48h and total amount of fentanyl within postoperative 48 h for PCIA were compared. Results: (1) Distribution of 3 genotypes in group U (n=37) was: 86.5% of GG, 10.8% cases of GA and 2.7% of AA; and in group H (n=34) was: 50% of GG, 44.1% of GA, and 5.9% of AA. In group U, allele G accounted for 91.9% while allele A accounted for 8.1%; in group H, allele G accounted for 72.1% while allele A accounted for 27.9%; and there were statistically significant differences between the two groups (P<0.05). (2) There were no statistically significant differences between two groups of patients in pulse oxygen saturation (Sp02), Ramasay scores and VAS scores at each time point. (3) Total amount of fentanyl within 48h of PCIA in group U was significantly greater than that of group H (P < 0.05). And total amount of fentanyl within 48h of PCIA in patients with mutant of CYP3A4*1G (GA+AA) of the two groups were significantly lower than that of the patients with wild GG genotype (P<0.05). Conclusions: There are ethnic differences between Xinjiang Uygur and Han nationality in polymorphism of CYP3A4*1G, which may be the main factor that causes differences between nationalities in postoperative analgesic effects of fentanyl.