Objective To investigate the effect of nutritional support on nutritional status and prognosis of patients with mechanical ventilation(MV) in acute exacerbation of chronic obstructive pulmonary disease(AECOPD). Methods Using randomized method,100 MV patients in AECOPD were divided into treatment group and control group. In 48 hours after MV, the treatment group(n=50) was given enteral nutrition (EN) ; the control group(n=50) were given self-made liquid food. The nutritional indicators were monitored before treatment and days 7 and 14 days of treatment, including arm muscle circumference (AMC), serum albumin (ALB), prealbumin (PA), hemoglobin (Hb), nitrogen balance (NB).The nutritional status was assesses including body mass index (BMI), triceps fold thickness (TSF), arm muscle circumference (AMC); The immunological parameters were observed including immunoglobulin A (IgA). The clinical indicators were evaluated including weaning success rate, MV time, ICU time, the incidence of ventilator-associated pneumonia (VAP). The APACHE Ⅱ score and intolerance to EN were recorded, including the incidence of gastric retention, regurgitation, and aspiration, catheter-related infection, and the incidence of other related adverse events. At the same time, patients who did not reach the endpoint (death occurred or abandoned treatment) were withdrawn from treatment. Results Compared with before treatment, the serum ALB, PA, Nb and IgA of the patients in the treatment group were significantly higher than those in control group on day 14 of treatment (all P<0.05); BMI, TSF and AMC in the treatment group were significantly improved (all P<0.05); APACHE Ⅱ score in the treatment group was significantly improved (all P<0.05). Compared with the control group, the MV time, ICU time and the incidence of VAP in the treatment group were significantly lower (P<0.05); and the weaning success rate within 2 weeks in the treatment group was significantly higher (P<0.05). Adverse events occurred in both groups, but there was no statistical significance. There were patients with withdrawal from both group, four in the treatment group and 10 in the control group. No comparison of relevant indicators was conducted among all patients with withdrawal. Conclusion For MV patients in AECOPD, EN is an important measure. It can improve the nutritional status, better promote protein synthesis, improve the body immunity, comprehensively improve the therapeutic effect and improve the prognosis of patients.