Ulcerative colitis is an inflammatory bowel disease whose pathogenesis has not been fully understood so far. The clinical manifestations are mainly abdominal pain, diarrhea, mucopurulent stools and urgency, and the severity of the disease varies. A few cases may be complicated by toxic megacolon, fistula and intestinal perforation. The pathological changes are mainly confined to the mucosa and submucosa of the colon, but in severe cases, the muscle and plasma layers may be invaded, mainly involving the rectum and sigmoid colon, and in a few cases, the whole colon. The mucosa is diffusely congested, edematous, brittle and prone to bleeding, with granular lesions and pseudo-polyps, and more than 95% are multiple ulcers. It is believed that the pathogenesis of ulcerative colitis is the result of multifactorial interactions, mainly including genetic, infectious, environmental and immune factors. Clinical treatment commonly uses three types of drugs: salicylic acid, steroids and immune agents, with an overall efficiency of 70% to 80%. In recent years, the disturbance of the normal bacterial flora present in the human intestine is considered to be an important factor in the pathogenesis of inflammatory bowel disease, and the disturbed intestinal flora can stimulate damage to the intestinal epithelium, increase the permeability of the intestinal mucosal barrier, and affect the immune system of the intestinal mucosa to produce persistent inflammation of the intestine. To prove this, medical scientists made animal models of intestinal aseptic state, then imposed various possible factors that induce inflammatory bowel disease, and finally found that after restoring normal flora to the animals, intestinal inflammation appeared, and the use of antibiotics again reduced the occurrence of intestinal inflammation. Based on the results of this experiment, foreign scholars added amoxicillin, tetracycline and metronidazole to the treatment of ulcerative colitis right along with the application of immune preparations and salicylates, which led to a significant improvement in the therapeutic effect. Ozone is a kind of reactive oxygen, which has strong oxidizing property, and its application in medical field is called triple oxygen therapy, which is a medical method developed along with “bio-oxidation therapy” in recent years. Compared with antibiotics, trioxane is a physical method to kill bacteria without the influence of drug resistance and at low cost. Several scholars in China have combined trioxin rectal infusion to treat nearly 100 cases of ulcerative colitis patients, resulting in a significant increase in the efficacy of traditional treatment methods. Recently, our Gastroenterology Department of Shanghai Public Health Clinical Center received a case of a farmer in Jinshan District, who had visited several hospitals, taken a variety of drugs, and treated for several years, but her condition was sometimes good and sometimes bad. We also added trioxin rectal irrigation to the traditional treatment method, and shortly after treatment, this patient’s stool frequency decreased significantly, bloody stools gradually reduced until they disappeared, and multiple ulcers in the rectosigmoid colon subsided on re-examination by colonoscopy. Although, the effectiveness of 1 patient does not indicate that a statistically large sample of many patients is also effective, it has shown beneficial effects in relieving patients’ suffering as a supplement to conventional treatment. Trioxane is very soluble in water and has 13 times the solubility of oxygen and 25 times the solubility of air at one standard air pressure at room temperature. The reason why trioxane rectal infusion therapy for ulcerative colitis can show efficacy is based on three principles: 1) Systemic effect: trioxane is absorbed into the blood circulation through the intestinal mucosa, and trioxane can react with tissues (especially blood) to improve the metabolism of red blood cells, such as activating the oxidative bypass of sugar (pentose phosphate bypass), increasing the content of 2,3-diphosphoglycerate in red blood cells, and 2,3 diphosphoglycerate enters the molecular structure of hemoglobin and simultaneously excludes the release of four oxygen molecules, the affinity of hemoglobin for oxygen molecules decreases, the hemoglobin oxygenation curve shifts to the right, and the tissue oxygenation effect increases. Trioxane also has immune activation and immunomodulatory effects, affecting the pathological immune mechanism of ulcerative colitis pathogenesis by inducing cells to produce a variety of cytokines; 2) local effects: trioxane can disrupt bacterial cell membranes, react with substances in the cytoplasm, and react with bacterial DNA, opening the DNA double strand, thus inhibiting bacterial proliferation, promoting the healing of lesions, and restoring the pathogenic microorganisms caused by intestinal flora dysbiosis; 3) Trioxane can reduce blood viscosity, improve microcirculation, and facilitate the absorption of inflammation and tissue repair. As we all know, any treatment method has its strict indications and contraindications, and triple oxygen therapy is no exception. High concentrations of trioxane are prohibited for direct inhalation into the lungs because trioxane can damage alveolar epithelial cells. In addition, trioxane has the effect of activating metabolism in the body. Patients with hyperthyroidism are contraindicated for trioxane therapy, as is glucose-6-phosphate dehydrogenase deficiency, or sericea, because the erythrocytes of patients with this disease lack an antioxidant protection system, which can lead to massive destruction of erythrocytes when in contact with trioxane. Gaseous trioxane is extremely unstable at room temperature and pressure in the syringe and will decompose quickly, so fresh trioxane must be applied immediately to achieve therapeutic results. Therefore, trioxane therapy must be performed in a hospital and cannot be used as a drug that can be taken home. Trioxin rectal infusion combined with traditional methods for the treatment of ulcerative colitis is a simple and safe method, and will certainly be of great interest as its basic and clinical research is further developed.