Mesalazine can treat rectal erosion, the types of oral mesalazine enteric-coated tablets and local use of mesalazine suppositories, patients under the guidance of the doctor oral mesalazine and with mesalazine suppositories rectal administration can achieve good therapeutic effect. Mesalazine’s active ingredient is 5-aminosalicylic acid, is an anti-inflammatory drug, its anti-inflammatory mechanism is not completely clear, studies show that mesalazine on the intestinal mucosal prostaglandin content has a certain effect, has the function of scavenging reactive oxygen radicals, lipoxygenase may play a certain role in the inhibition of lipoxygenase, to play an anti-inflammatory role in the repair of the mucous membrane erosion. Adverse effects of mesalazine include rash, diarrhea, arthralgia, and malaise. It should be noted that contraindications are the presence of severe renal failure and hypersensitivity to salicylates. The dosage should follow the doctor’s instructions. In conclusion, during the treatment period, patients should use mesalazine under the guidance of the doctor, the occurrence of adverse reactions promptly communicate with the doctor to avoid serious consequences.