Anastomotic-transverse colon fistula after Roux-en-Y gastrojejunal anastomosis is very rare. Early symptoms of patients are not obvious and easy to be missed and misdiagnosed. Typical triad symptoms include diarrhea, weight loss, fecal vomiting or fecal belching. According to digestive tract radiography and gastrointestinal endoscopy, patients with definite diagnosis should be treated as soon as possible under the premise of improving nutritional status. In this patient, the disease was diagnosed by upper gastrointestinal radiography and gastroscopy. After active preoperative preparation and one-stage surgery, the symptoms were significantly improved. The Center′s diagnosis and treatment process and treatment experience for the disease are reported as follows.