Clinically mesalazine is a common drug used in the treatment of inflammatory bowel disease. For acute exacerbations, it is generally recommended for two to three months. For the remission phase it is generally recommended to be applied for three to five years, or even for life. Mesalazine is clinically composed of 5-aminosalicylic acid. It is commonly used as a treatment drug for Crohn’s disease or ulcerative colitis and is one of the basic drugs for this disease. For acute exacerbations a loading dose, i.e. 4g per day for oral administration, can be considered and the dose is reduced by half during remission. If the patient is clinically mild, good results can usually be achieved with single drug control. In addition, the drug is applied for a long period of time, so patients must follow medical advice, and the effect of the drug is usually judged in conjunction with the patient’s clinical symptoms and colonoscopy results. However, moderate to severe patients may need a combination of hormones or biological agents, probiotics and other drugs for comprehensive treatment. In addition, there are certain contraindications to the clinical use of mesalazine. It should be prohibited for patients with gastrointestinal bleeding or patients with severe liver and kidney dysfunction, and patients should pay attention to take it as prescribed by their doctors and should not increase or decrease the dose by themselves.