The purpose of this study are as follows: 1) To evaluate the efficacy and safety of Qizhi Weitong granules in the treatment of diarrhea-type irritable bowel syndrome (IBS-D);2) To explore the dosage of Qizhi Weitong Granulesin treatment of IBS-D.

Inclusion Criteria:

• In line with the diagnostic criteria of WESTERN medicine IBS-D;
• Aged 18-65 (including 18 and 65 years old) years;
• The mean weekly NRS score for abdominal pain (the most severe in the past 24 hours) was between 3.0 and 7.0 within the last week, and there were at least 2 days per week when fecal traits were classified as type 6 or 7;
• Informed consent, voluntary test.

Exclusion Criteria:

• Stool number of type 7 according to Bristol Stool Chart, more than 3 times per day;
• TCM syndrome was diagnosed as deficiency of spleen and kidney Yang syndrome；
• Patients who took emergency medication (Piveronium bromide tablets) more than the standard during admission period (more than 2 days per week on average)；
• Patients who have been diagnosed with organic diseases of digestive system, such as inflammatory bowel disease, intestinal tuberculosis, intestinal tumor, etc., or are still complicated with peptic ulcer and infectious diarrhea；
• Patients with similar symptoms of IBS, such as eosinophilic enteritis, collagenous enteritis, lactose intolerance, etc.
• Patients with intestinal diseases of digestive system, such as tuberculous peritonitis, cirrhosis, chronic pancreatitis, etc.
• Patients with systemic diseases affecting digestive tract function, such as hyperthyroidism or hypothyroidism, endometriosis, chronic renal insufficiency, autoimmune diseases, diabetes, etc.
• Previous gastrointestinal surgery (except for appendicitis);
• Patients with serious cardiovascular diseases, serious liver and kidney diseases, hematopoietic system diseases, tumor, neurological or psychiatric system diseases;
• Major anxiety (SAS score ≥70) or major depression (SDS Score ≥73);
• Concomitant drugs affecting gastrointestinal motility and function (prokinetic drugs, anticholinergic drugs, calcium channel blockers, 5-HT3 receptor antagonists, antidiarrhea agents, antacids, antidepressants, antianxiety drugs, intestinal microbiota regulators, antibiotics, etc.) should not be discontinued in the test;
• Pregnant or lactating women who had a birth plan from enrollment to 3 months after the end of the trial.
• Allergic to the test drug emergency drug and its ingredients;
• Suspected or confirmed history of alcohol or drug abuse;
• Patients who participated in other clinical trials within 1 month prior to enrollment;
• Other subjects considered unsuitable for clinical trials by the researchers.