Abstract: Objective To explore the effect of low dose sulfentanyl on labor analgesia. Methods 90 puerperas were randomly divided into observation group,control group I and control group Ⅱ,30 cases in each group.Sulfentanyl was used for labor analgesia in all the groups.The dose of sulfentanyl in the control group Ⅰ,the observation group and control group Ⅱ were 3 μg, 5 μg and 7μg respectively.Indexes such as analgesic efficacy,maternal birth outcomes,adverse re-actions and neonatal state were compared among three groups.Results The onset time of analge-sia in the control group Ⅰ was significantly longer than that in the observation group or the control group Ⅱ (P <0.05),while the first agent duration was significantly shorter than that in the ob-servation group or the control group Ⅱ (P <0.05);before the analgesia,there was no significant difference of VAS score among three groups (P >0.05);at the time of 30 and 60 minutes after analgesia,the VAS score of the control group I was significantly higher than that of the other two groups (P <0.05);there were no significant differences of the vaginal delivery rate,assistant vaginal delivery rate and cesarean section rate among the three groups (P >0.05);the incidence rates of the adverse reactions such as pruritus,nausea and vomiting,lethargy and fetal heart changes of the women in the control group Ⅰ and the observation group were significantly lower than those in the control group Ⅱ (P <0.05);the Apgar scores of the neonates in the control group Ⅰ and the observation group were significantly higher than that in the control group Ⅱ (P<0.05).Conclusion Efficacy of high or low dose sulfentanyl for labor analgesia is similar,while a very low dose sulfentanyl can not achieve the desired results.Compared with a high dose sulfen-tanyl,the adverse reactions probability induced by a low dose sufentanil is low and the neonatal state is better.