Vomiting dark green liquid in patients with advanced small bowel cancer may be caused by factors such as adverse drug reaction and cancerous intestinal obstruction. 1. Adverse drug reaction: If patients with advanced small bowel cancer are receiving treatment, it may be due to the adverse reaction of drugs used by patients, which leads to nausea and vomiting symptoms, and then bile will be vomited, so patients with advanced small bowel cancer will vomit dark green liquid. 2. Cancerous intestinal obstruction: Vomiting dark green liquid in patients with advanced small bowel cancer may be due to intestinal obstruction caused by tumor, and when gastrointestinal reaction occurs in the intestine after obstruction, there will be vomiting of bile, and the bile will be dark green liquid. If patients with advanced stage of small intestine cancer vomit dark green liquid, it is recommended to go to the hospital in time, and under the doctor’s judgment, clarify the cause of the disease and carry out targeted treatment, so as not to aggravate the disease and cause serious impact on the patients.