Objective To analyze the effect of probiotics combined with early enteral nutrition on infection and gastrointestinal dysfunction in patients undergoing mechanical ventilation in intensive care unit (ICU). Methods Prospective cohort study was adopted to select patients who admitted to ICU in a hospital from February 2016 to October 2017, they were randomly divided into three groups:A, B, and C. Group A received early enteral nutrition combined with probiotics, group B received early enteral nutrition, and group C received early parenteral nutrition. Infection condition, level of infection indicators (on the 3rd, 7th and 14th day after treatment), occurrence of gastrointestinal dysfunction, acute physiology and chronic health evaluation Ⅱ (APACHE Ⅱ) on the 14th day after treatment were compared among three groups. Results Incidences of infection in group A, B, and C were 6.00%, 20.00%, and 22.00% respectively, difference among three groups was significant (χ²=8.57, P=0.01). C-reactive protein (CRP) and white blood cell count (WBC) in group A on the 7th and 14th day were both lower than those in group B and C; procalcitonin (PCT) in group A and B on the 3rd day were both lower than that in group C; PCT in group A on the 7th and 14th day were both lower than those in group B and C; difference were all statistically significant (all P< 0.05). Incidence of abdominal distension (8.00%), diarrhea (4.00%) and gastric retention (4.00%) in group A were the lowest among three groups. APACHE Ⅱ score in group A on the 14th day after treatment was lowest. Conclusion Early enteral nutrition combined with probiotics for treatment of ICU patients with mechanical ventilation can effectively reduce the incidence of infection and gastrointestinal dysfunction, promote rehabilitation, which is worth promoting the application.