Magnesium salts such as magnesium citrate are often combined with polyethylene glycol to make the intestinal preparation before colonoscopy, which has shown high cleaning efficacy. Magnesium sulfate combined with polyethylene glycol is less used in the world. This multicenter, randomized, controlled trial is aimed at to evaluate the efficacy and safety of magnesium sulfate combined with low-volume polyethylene glycol for preoperative bowel preparation for colonoscopy.

Inclusion Criteria:

• 18-75 years old, male or female
• To undergo screening, surveillance and diagnostic colonoscopy
• Signed written informed consent

Exclusion Criteria:

• Subjects with therapeutic colonoscopy for colorectal polyps
• Subjects with confirmed or suspected gastrointestinal obstruction, gastric retention, gastroparesis, gastric emptying disorder, or acute gastrointestinal bleeding
• Subjects with confirmed or suspected colorectal cancer, inflammatory bowel disease, toxic colitis, or toxic megacolon
• Subjects with renal or liver dysfunction, congestive heart failure or rhabdomyolysis
• Subjects with ascites, suspected electrolyte abnormalities, or uncorrected dehydration
• Subjects with constipation (<3 times a week, difficult defecation, dry stool, less amount)
• Subjects with serious cardiac and cerebrovascular diseases,suffering from metabolic disease or endocrine disease
• Subjects who had previously undergone colorectal resection
• Women with positive pregnancy tests or pregnancy plans, and women in lactation or allergic to the investigational drugs and their ingredients
• Subjects who are participating in other clinical trials or receiving special drugs
• Subjects with any other conditions that the investigator considered inappropriate for inclusion