This trial is a randomized, double-blind, placebo-controlled, parallel-group, multicenter Phase III clinical trial. Its purpose is to evaluate the efficacy and safety of Changji'an Capsules in subjects with diarrhea-predominant irritable bowel syndrome (liver-qi invading spleen syndrome) after 8 weeks of treatment.

Inclusion Criteria:

1. Meet the Western medicine diagnostic criteria for diarrhea-predominant irritable bowel syndrome;
2. Meet the Traditional Chinese Medicine syndrome differentiation criteria for liver Qi invading the spleen;
3. Aged ≥18 and ≤65 years, regardless of gender;
4. Record daily the most severe abdominal pain, bloating, and abdominal discomfort NRS scores for the last week of the run-in period. At least one of these three items must meet the weekly average NRS score criterion (the weekly average of abdominal pain NRS is calculated as: total weekly score of abdominal pain NRS on days with Bristol Stool Form Scale type 6 or 7 stools / actual number of days with Bristol type 6 or 7 stools in that week; the average values for the other two items are calculated similarly) ≥3 points (11-point Numerical Rating Scale, NRS-11); meanwhile, for stool form, during the last week of the run-in period, there must be at least 2 days in which each day has at least one bowel movement of Bristol type 6 or 7;
5. Self-Rating Anxiety Scale (SAS) <60 points and Self-Rating Depression Scale (SDS) <63 points;
6. Have a colonoscopy result showing no obvious abnormalities (including diverticula or chronic inflammation) or colon polyps, based on colonoscopy results within 12 months prior at a tertiary hospital: 1.Colonoscopy results are normal with no organic changes; 2. Colonoscopy report shows minor abnormalities such as hemorrhoids or colonic polyps (diameter ≤5mm and number ≤3), which the investigator deems eligible for inclusion; 3. Previous colonoscopy reported colonic polyps with diameter >5mm or number >3, but after endoscopic treatment within 6 months prior to screening, remaining polyps are ≤5mm in diameter and ≤3 in number, deemed eligible by the investigator;
7. Agree to participate in this clinical trial and voluntarily sign the informed consent form.

Exclusion Criteria:

1. Individuals with fewer than 3 spontaneous bowel movements per week during the induction period;
2. Individuals with stool consistency of type 1 or 2 (Bristol Stool Form Scale) on at least 2 days per week during the induction period;
3. Individuals confirmed to have infectious diarrhea, inflammatory bowel disease, parasitic infection, positive fecal occult blood tests and considered to have gastrointestinal bleeding (excluding hemorrhoids), colorectal tumors, malabsorption syndrome, lactose intolerance (based on medical history), and diarrhea caused by systemic diseases;
4. Individuals who have used other medications for irritable bowel syndrome within 1 week prior to screening;
5. Individuals with non-IBS-D or other organic gastrointestinal lesions (excluding superficial gastritis, grade I erosive gastritis, or chronic atrophic gastritis found on endoscopy but deemed by the investigator to be eligible for inclusion (e.g., no mucosal erosion or bleeding observed endoscopically, and the patient has no upper abdominal fullness, upper abdominal pain, or acid reflux)), or other organic lesions that the investigator judges may cause abdominal pain, bloating, or discomfort;
6. Individuals with diabetes, hyperthyroidism, or serious primary diseases of the cardiovascular, cerebrovascular, liver, kidney, hematopoietic systems, or other serious diseases affecting survival (e.g., tumors), abnormal liver and kidney function (AST, ALT > 1.5 times the upper limit of normal reference range, Scr above the upper limit of normal reference range), and clinically significant ECG abnormalities;
7. Individuals with other mental disorders (excluding mild anxiety or depression);
8. Individuals with a history of gastrointestinal surgery (excluding appendectomy or intestinal polyp removal);
9. Individuals who, within 2 weeks prior to screening, are using or need to continue using medications that may affect gastrointestinal function (anticholinergic drugs, 5-HT3 receptor antagonists, antidiarrheal drugs, antacids, prokinetic drugs, antidepressants (fluoxetine for at least 28 days), anti-anxiety drugs, intestinal microbiota regulators, traditional Chinese medicine decoctions, etc.);
10. Individuals allergic to 3 or more medications or foods, or known allergies to Xiangjie Capsules and its components, as well as emergency medication Pivabromium tablets;
11. Individuals who took emergency medication (Pivabromium tablets) during the last week of the induction period;
12. Individuals who took prohibited medications during the induction period;
13. Individuals suspected of or confirmed with a history of alcohol or drug abuse;
14. Pregnant women, breastfeeding women, or women of childbearing age planning to conceive; or female participants of childbearing potential and male participants (whose partners are women of childbearing potential) who do not agree to voluntarily use effective contraception from screening to 3 months after the last dose;
15. Individuals with cognitive impairment unable to provide fully informed consent;
16. Individuals positive for hepatitis B surface antigen, HIV antibody, hepatitis C antibody, or syphilis treponemal antibody;
17. Individuals who have participated in another clinical trial within the past month;
18. Individuals known to have familial colorectal cancer syndrome;
19. Individuals who, in the opinion of the investigator, have other factors making them unsuitable for inclusion.