This study intends to evaluate the effects of three prebiotic solid beverages (mainly dietary fiber and prebiotics) and one probiotic solid beverage on the laxative effect of patients with functional constipation through randomized controlled trials. The influence of tract flora is expected to provide a basis for related therapies for patients with functional constipation.

Inclusion Criteria:

1. Adults: 18 to 70 years old (not less than 50% of the final population over 45 years old, and not less than 30% of men);
2. Patients with functional constipation (refer to Rome IV diagnostic criteria for functional constipation); * Symptoms appeared for at least 6 months before diagnosis, and met the above diagnostic criteria in the past 3 months

Exclusion Criteria:

1. Pregnant and lactating women;
2. Unable to take the test sample and complete the inspection items as required due to inability to take food by mouth, weakness, allergies or other reasons (including the inability to complete all items due to recent travel plans);
3. Unclear main complaint and obvious abnormal mental state;
4. The liver and kidney function indexes are obviously abnormal (combined with the results of physical examination within the past 1 year);
5. Acute gastrointestinal diseases occurred in the past month, and constipation caused by surgical operations in the past month;
6. Take antibiotics, laxatives or topical agents, anticholinergics, antidiarrheals frequently in the past 1 month, and the frequency is more than 1 time/week
7. Have been diagnosed with the following diseases: cancer (especially cancer of the digestive tract), severe enteritis, intestinal obstruction, inflammatory bowel disease, hypothyroidism, mental illness;
8. Have been diagnosed with the following diseases: severe systemic diseases such as stroke, heart disease, liver cirrhosis, renal failure, hematopoietic system, or qualitative intestinal diseases caused by colonoscopy or imaging display;
9. In the past 3 months, there are often abdominal pain, abdominal pain accompanied by changes in bowel characteristics or frequency, blood in the stool, diarrhea or involuntary weight loss;
10. Clinical manifestations or diseases that other researchers believe are not suitable for participating in the project.