Abstract： Objective： To observe the curative effect of modified Liangdi tang combined with dydrogesterone for threatened abortion with yin deficiency and blood heat syndrome. Methods：A total of 68 cases of patients with threatened abortion were selected and divided into two groups according to random number table method，34 cases in each group. The control was given dydrogesterone tablets， and the observation group was given modified Liangdi tang combined with dydrogesterone. Both groups were continuously treated for two weeks. The disappearance time of symptoms and signs and clinical effect were compared between the two groups. Before treatment and after two-week treatment，symptoms of yin deficiency and blood heat syndrome and changes in levels of serum hormones were observed in the two groups. Results： After two-week treatment，the total effective rate was 97.06% in the observation group，and 76.47% in the control group， the difference being significant(P＜0.05). The disappearance time of abdominal pain，low back pain，uterine contraction，and vaginal bleeding in the observation group was earlier than that in the control group(P＜0.01). Scores of bearing- down and distending pain of low back and abdomen，scores of vexing heat in the chest，palms and soles，scores of dry mouth and throat，scores of scanty yellowish urine，and scores of hard bound stool in the two groups were decreased when compared with those before treatment(P＜0.01)，and the scores in the observation group were all lower than those in the control group (P＜0.01). Levels of estradiol(E2)，progesterone(P)，and human chorionic gonadotropin(HCG) in serum in the two groups were increased when compared with those before treatment(P＜0.01)，and the three levels in the observation group were higher than those in the control group(P＜0.01). Conclusion：The therapy of modified Liangdi tang combined with dydrogesterone tablets has a significant curative effect in the treatment of threatened abortion with yin deficiency and blood heat syndrome. It can help promote the relief of symptoms and signs and effectively improve the hormone levels of patients.