【Abstract】 Objective To investigate the effect of preemptive injection of Dufei mixture (pethidine 100 mg and promethazine 25 mg) on the outcome of vaginal delivery. Methods 90 full-term primiparas without medical complications in the delivery records of our hospital from January 2018 to August 2018 were selected for retrospective analysis. The pregnant women were given Dufei mixture in the incubation period were divided into injection group (45 cases) and control group (45 cases) respectively. The differences of the duration of labor, the amount of vaginal bleeding, the rate of amniotic fluid fecal staining and the Apgar score of the newborn between the two groups were compared. Results The duration of first and total stage of labor of injection group were longer than that of control group, and the difference showed statistically significance. The fecal staining rate of amniotic fluid of injection group was lower than that of control group. Difference between the duration of second stage of labor, the amount of postpartum bleeding (in 2hrs), and newborn Apgar score of injection group and control group showed no statistically significance. Conclusion It is reliable and safe to employ pethidine hydrochloride and promethazine hydrochloride as the labor analgesic drug in the incubation.