Objective To explore the effect of Huoxue Fang on disintegration of endometrium and possible mechanism. Methods Totally 130 C57 BL /6J female mice were divided into sham operation group（ n = 10）

model group（ n = 60） and herb group（ n = 60）. Model and herb group were given sequential hormone to replicate models of menstruation bleeding mice. Induce decidualization to left uterine cavity. From the ninth day of modeling

herb group were given Huoxue Fang 20 g /（ kg·d） by gavage. Sham operation group and model group were given equivalent normal saline. After progesterone withdrawals at 0

8

12

16

24

32 h

choose a certain amount of mice in both groups respectively to take vaginal secretion detection and observe disintegration and shedding of endometrium. After hematoxylin-eosin（ HE） staining

observe pathological change of bilateral uterine horn and calculate uterine coefficient. Detect the expression of MMP3、MMP9、P50 and P65 in uterine tissues adopting immunohistochemical method. Detect the expression of MMP3 mRNA and MMP9 mRNA with Real-time PCR. Detect the protein expression of MMP3 and MMP9 and the nuclear protein expression of P50 and P65 in uterine tissues using Western blot. Results Compared with sham operation group

left side of uterine of model group mice showed significant pathological change.From 12 h

the rate of bleeding mice increased; left uterine coefficient increased significantly（ P < 0. 05）. Compared with model group

bleeding time-histories of herb group decreased obviously; at 0

8

12 h

left uterine coefficient increased which decreased at 32 h（ P < 0. 05）. Compared with model group

the expression of MMP3 mRNA and MMP9 mRNA of left uterine tissues of herb group were up-regulated obviously during 0- 32 h（ P < 0. 05）. The expression of MMP3 and MMP9 protein increased during 0- 12 h and were down-regulated at 32 h（ P < 0. 05）.Compared with model group

nuclear protein P50 of left uterine tissues of herb group mice was up-regulated at 0 and12 h and was down-regulated at 8

16

24

32 h（ P < 0. 05）. Nuclear protein P65 was up-regulated at 0

12

24 h and was down-regulated at 32 h（ P < 0. 05 or P < 0. 01）. Conclusion Huoxue Fang can decrease disintegration time-histories of endometrium. The mechanism may relate to expression of MMP3 and MMP9 and rapid activation and timely closure of NF-κB pathway.