To evaluate the efficacy and safety of motherwort (herba leonuri/leonurus heterophyllus sweet) injection for preventing postpartum hemorrhage after caesarian section. The prospective study was designed as a randomized and single blind multi-center research matched with positive agent as controls from Apr 2007 to Aug 2007. 440 women underwent caesarian section (CS) indicated by obstetric factors were enrolled from 15 teaching hospitals in China and assigned into three groups: group of motherwort: 147 cases were administered by motherwort 40 mg uterine injection during CS and 20 mg intramuscular injection per 12 hours 3 times after CS; group of motherwort+oxytocin: 144 cases were administered by motherwort 40 mg and oxytocin 10 U uterine injection during CS and motherwort 20 mg intramuscular injection per 12 hours 3 times after CS and group of oxytocin: 149 cases were administered by oxytocin 10 U uterine injection and oxytocin 10 U+5% glucose 500 ml intravenously injection during operation and oxytocin 10 U intramuscular injection per 12 hours 3 times after CS. The following clinical parameter were collected and analyzed: (1) The amount of blood loss during operation, at 2, 6, 12, 24, 48 hours after operation. (2) The total amount of blood loss in 24 hours after CS and the incidence of postpartum hemorrhage. (3) The change of level of hemoglobin (Hb) and counting of red blood cell (RBC) from prepartum to postpartum. (4) Adverse reaction. (1) The mean amount of blood loss during operation were (368+/-258) ml in group of motherwort, (255+/-114) ml in group of motherwort+oxytocin and (269+/-141) ml in group of oxytocin, which exhibited significant difference among three groups (P<0.01). Meanwhile, no statistical different amount of blood loss among three groups were observed at 2, 6, 12, 24, 48 hours after CS. (2) The amount of blood loss of postpartum at 24 hours were (480+/-276) ml in group of motherwort, (361+/-179) ml in group of motherwort+oxytocin, (381+/-179) ml in group of oxytocin, which showed significant difference among 3 groups (P<0.01). (3) The incidence of postpartum hemorrhage were 32.0% (47/147) in group of motherwort, 11.1% (16/144) in group of motherwort+oxytocin, and 18.8% in (28/149) in group of oxytocin. When comparing the lowest rate of postpartum blood loss in group of motherwort+oxytocin and the highest rate in group of motherwort, it displayed statistical difference (P<0.01). (4) The decreased level of RBC and Hb were shown that RBC (0.3+/-0.5)x10(12)/L and Hb (9+/-13) g/L in group of motherwort, RBC (0.2+/-0.4)x10(12)/L and Hb (6+/-10) g/L in group of motherwort+oxytocin and RBC (0.2+/-0.4)x10(12)/L and Hb (7+/-30) g/L in group of oxytocin respectively. However, the comparison of different value of RBC and Hb in group of oxytocin and motherwort+oxytocin showed significant difference (P<0.05). (5) Two cases with allery reaction was observed. It is safe and efficacious that combined use of motherwort injection and oxytocin was to prevent postpartum hemorrhage during or after caesarian section.