AIM To observe the clinical efficacy of Maixuekang Capsules (hirudin) combined with female progestational hormone treating blood-stagnated cryptogenic hypomenorrhea and their mechanism of action.METHODS Ninty eligible patients were randomly and equally divided into treatment group (Maixuekang Capsules combine with female progestational hormone) and control group (female progestational hormone),treated for three menstrual cycles,the menstrual blood volume,blood D-dimer,maximum platelet aggregation rate,the thickness of endometrium,spiral artery blood flow peak systolic velocity (PSV),resistance index (RI) and pulsatility index (PI) were recorded during the three months period.RESULTS The menstrual blood volume of the two groups were all increased post-treatments (P ＜ 0.05),the treatment group was superior to the control group (P ＜ 0.05);blood D-dimer and maximum platelet aggregation rate of the treatment group had reduced post-treatments (P ＜ 0.05),there was no difference in the two values of the control group between post-treatment and pre-treatment (P ＞ 0.05);the thickness of endometrium of the two groups were both increased after the treatment (P ＜ 0.05),while there was no remarkable statistical difference between the two groups (P ＞ 0.05);RI in the treatment group had remarkable reduction post-treatments (P ＜ 0.05),but there was no remarkable difference of RI in the control group (P ＞ 0.05);there was no statistical difference of PSV and PI in both groups before and after the treatment (P ＞ 0.05).CONCLUSION The combination treatment of Maixuekang Capsules and female progestational hormone can obviously increase menstrual blood volume,improve uterine blood perfusion and endometrial microcirculation.It has more advantages than use hormones alone.