Objective To investigate the clinical characteristics, risk factors and perioperative outcome of prolonged mechanical ventilation (PMV) in elderly patients undergoing coronary artery bypass grafting (CABG). Methods The data of elderly patients receiving CABG in the Nanjing First Hospital from January 2013 to June 2019 were collected. All patients were divided into a control group and a PMV group according to whether ventilation time≥24 h.The clinical characteristics and risk factors of PMV were compared between the two groups. Variables were 1∶1 balanced through propensity score matching (PSM) and perioperative outcomes of two groups was analyzed. Results Finally 956 patients were collected, including 187 in the PMV group and 769 in the control group. There were 586 males and 370 females aged 70-94 (74.3±3.5) years. Compared with the control group, the PMV group had higher rates of smoking, preoperative renal impairment, intraoperative blood transfusion and intra-aortic balloon pump (IABP) implantation, worse cardiac function, lower glomerular filtration rate and ejection fraction, larger left atrial diameter, longer cardiopulmonary bypass time and aortic cross-clamping time (P<0.05). There was no statistical difference in other clinical data between the two groups (P>0.05). Binary multivariate logistic regression analysis showed that females, smoking, chronic obstructive pulmonary disease, left ventricular ejection fraction≤56.0%, cardiopulmonary bypass time>106.0 min, IABP implantation and intraoperative blood transfusion were independent risk factors for PMV in elderly patients. After PSM, there were 146 patients in the control group and the PMV group, respectively. The PMV group had longer ICU stay and length of hospital stay and more drainage volume compared with the control group (all P<0.05). There was no statistical difference in perioperative mortality or other complications between the two groups (all P>0.05). ConclusionThere are a lot of factors associated with PMV of the elderly patients undergoing on-pump CABG. In order to establish a complete and formal PMV prediction model, clinicians can make a further step of assessment according to perioperative elements, and improve the prognosis of such patients.