Using a placebo as a control, this study aims to preliminarily evaluate the clinical efficacy of Congrong Runtong oral liquid for the treatment of functional constipation (Yang-deficiency type), explore the optimal dosage of Congrong Runtong oral liquid for functional constipation (Yang-deficiency type) to provide a basis for dosage selection in Phase III clinical trials, and observe the safety of clinical use of Congrong Runtong oral liquid.

Inclusion Criteria:

1. Meets the Rome IV diagnostic criteria for functional constipation;
2. Meets the TCM diagnostic criteria for Yang-deficiency type constipation;
3. Aged between 18 and 70 years (inclusive);
4. Has undergone colonoscopy and has been diagnosed with either no abnormalities or non-adenomatous polyps (size not exceeding 0.5 cm, no more than 3) or has undergone polypectomy for more than 1 month and the pathological examination confirms no high-grade intraepithelial neoplasia within 12 months of colonoscopy examination in a tertiary grade A hospital
5. Less than 3 complete spontaneous bowel movements per week during the 2-week run-in period;
6. Voluntarily participates in the trial and signs an informed consent form.

Exclusion Criteria:

1. Patients with constipation caused by organic lesions of the rectum or colon (such as tumors, inflammatory bowel disease, anal fissure, intestinal adhesions, intestinal tuberculosis) leading to intestinal stenosis;
2. Patients with constipation caused by other systemic organic diseases, such as congenital megacolon, neurological disorders (such as autonomic neuropathy, cerebrovascular disease, etc.), mental disorders, metabolic endocrine disorders (such as hypothyroidism, diabetes mellitus with fasting blood glucose > 8.6mmol/L or with complications), muscular diseases (such as amyloidosis, dermatomyositis), etc.;
3. Patients whose drug-induced constipation cannot be ruled out by the investigators；
4. Patients with alarm signs judged by the investigator and unable to exclude malignant lesions by colonoscopy in the past three months;
5. ALT or AST ≥ 1.5 times the upper limit of the normal value, or Scr > upper limit of the normal value;
6. Patients allergic to the composition of the ingredients of the Cenruong Runtong oral solution or bisacodyl;
7. Pregnant or breastfeeding women, or women planning to become pregnant;
8. Patients who have participated in other clinical trials in the past 3 months;
9. Other situations judged by the investigator as inappropriate for participation in this trial.