Objective To investigate the effects of enteral nutrition support with glutamine combined with dietary fibre and fructo oligosaccharide (GFO) on nutritional status, gastrointestinal function and outcome in elderly patients with mechanical ventilation.Methods Totally 90 patients were randomly divided into three group: the control group without additives (group A), enteral nutrition group with glutamine (group B) or with GFO (group C).Fasting blood samples were collected on day 1, 7 and 14 after the initiation of study, and then the indicators including hemoglobin, albumin, transferrin and prealbumin were determined.In addition, the gastrointestinal complications including bloating, diarrhea, and gastric retention were observed, and the mechanical ventilation time, length of intensive care unit (ICU) stay and extubation time were recorded.Results The serum transferrin and prealbumin levels were significantly improved on the 7th day (P=0.023 and 0.047),and the hemoglobin was significantly improved on the 14th day (P=0.003).4 cases in group B and 3 cases in group C underwent successful implementation of enteral nutrition, and 25 cases in group B and 27 cases in group C achieved the target volume of enteral nutrition, which were more than those in group A (P=0.008 and 0.000 respectively).The incidence of gastrointestinal complication was less in groups B and C than in group A.The mechanical ventilation time, length of ICU stay and extubation time were shorter in groups B and C than in group A.Conclusions Enteral nutrition with glutamine and GFO can improve nutritional status and reduce gastrointestinal complications in elderly patients with mechanical ventilation.Enteral nutrition with GFO has an advantage to the enteral nutrition and the outcome.