Objective To investigate the value of Malnutrition Screening Tool (MST) in ventilated patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). Methods A single center retrospective observational study was conducted. The AECOPD patients who needed mechanical ventilation, admitted to ICU from January 2015 to June 2016 were enrolled in the study. They were divided into two groups according to the MST score, ie. a high risk malnutrition group (MST score≥2) and a low risk malnutrition group (MST score<2). The principle factors were analyzed including ICU mortality, in-hospital mortality, duration of invasive mechanical ventilation (IMV), length of ICU stay, and ICU readmission rate within 48 hours. Meanwhile the patients’ demographic and laboratory data were analyzed. Results A total of 101 patients were enrolled with 77 cases in the high risk malnutrition group and 24 cases in the low risk malnutrition group. The gender (χ2=1.882, P=0.172), age (t=1.091, P=0.33) and APACHE Ⅱ score (t=1.475, P=0.16) were similar in two groups. The high risk malnutrition group had significantly lower BMI (t=2.887, P=0.004) and lymphocyte count (t=3.402, P<0.001) than the low risk malnutrition group. Hemoglobin (t=0.817, P=0.36), albumin (t=0.706, P=0.44), pre-albumin (t=1.782, P=0.08) and procalcitonin (t=1.296, P=0.17) were similar in two groups. The high risk malnutritiongroup had significantly longer IMV duration (χ2=2.181, P=0.035) and length of ICU stay (χ2=2.364, P=0.02) than the low risk malnutrition group. While the ICU mortality (χ2=0.212, P=0.645), in-hospital mortality (χ2=0.212, P=0.645) and ICU readmission rate within 48 hours (χ2=1.656, P=1.0) were similar in two groups. Conclusion MST is a valuable tool in ICU to evaluated the nutrition status of ventilated AECOPD patients, and MST≥2 indicates longer IMV duration and length of ICU stay.