Previous researches demonstrated that a prepackaged low-residue diet (LRD) could achieve better bowel preparation quality compared with a self-prepared LRD. However, up to now, there has been no widely acceptable standard of LRD for bowel preparation. Moreover, these prepackaged LRD adopted in previous studies mainly consisted of traditional foods without further processing. Recently, a prepackaged LRD for Special Medical Purpose was specifically designed for bowel preparation. This trail was to compare the impact of the prepackaged LRD on bowel preparation for colonoscopy with self-prepared LRD by patients.

Inclusion Criteria:

• Patients whose age is between 18-65.
• Patients who have indications for screening, surveillance and diagnostic colonoscopy.
• Patients who have signed inform consent form

Exclusion Criteria:

• subjects who had known or suspected heart failure, stroke or renal failure;
• subjects who had a history of colon surgery or inflammatory bowel disease;
• subjects who Patients with had digestion or absorption dysfunction or any dietary restriction due to various reasons;
• subjects who had a history of hypersensitivity to any ingredients of laxatives or soy products;
• subjects who had high risk factors for bowel preparation such as chronic constipation, Body Mass Index (BMI) greater than 30 or BMI less than 18 Kg/m2, diabetes, spinal cord injury, or use of medications affecting bowel motility within a week;
• subjects who had participated in another interventional clinical trial in the previous 60 days;
• pregnant or lactating women and those planning to become pregnant.