Objective To observe clinical curative effects of modification of Zuojin Pills（左金丸） combined with Sini Powder（四逆散） in the treatment of diarrhea-predominant irritable bowel syndrome（ IBS-D） based on syndrome differentiation. Methods Randomly divided 144 cases of IBS-D into a treatment group and a control group

with 72 cases in each. The treatment group was divided into 4 syndrome patterns

including stagnation of liver Qi and spleen deficiency

dampness stagnancy due to spleen deficiency

spleen and kidney Yang deficiency

and intestinal hot and dampness

which were all given modification of Zuojin Pills combined with Sini Powder for treatment based on syndrome differentiation. The herbs were decocted in water for oral dose

one dose every other day. The control group took Otilonium Bromide Tablets 40 mg each time

three times per day. Two groups both took 15 days as one treating course

and were continuing treated for 4 courses. Abdominal pain and discomfort

frequency of diarrhea

simultaneous phenomenon scores of patients in two groups were observed before and after treatment. Curative effects on each symptom and comprehensive curative effects after treatment were judged. Results Single symptom scores of patients in two groups remarkably decreased after treatment compared with that before treatment（ P < 0. 05） Abdominal pain and discomfort

as well as simultaneous phenomenon scores in the treatment group were remarkably less than that in the control group（ P < 0. 05）. The curative effects on abdominal pain and discomfort

as well as simultaneous phenomenon in the treatment group were remarkably superior to that in the control group（ P < 0. 05）; Total effective rate of comprehensive curative effects was 86. 11% in the treatment group

remarkably higher than 79. 17% in the control group（ P < 0. 01）. There is statistical significant difference in total effective rates of comprehensive curative effects between each syndrome pattern in the treatment group（ P < 0. 05）. The total effective rate of the curative effect on stagnation of liver Qi and spleen deficiency syndrome was the highest one. Conclusions Modification of Zuojin Pills（左金丸） combined with Sini Powder（ 四逆散） can cure IBS-D effectively based on syndrome differentiation

especially for those with stagnation of liver Qi and spleen deficiency syndrome.