Objective To analyze the incidence and related factors of atelectasis in severe patients after hepatectomy. Methods A retrospective analysis was performed on 442 patients admitted to intensive care unit (ICU) after hepatectomy from 2014 to 2019 in Peking University People's Hospital. Patients were divided into atelectasis group (n=99) and non-atelectasis group(n=343) according to the occurrence of postoperative atelectasis. General information, complications, laboratory examination, operation, anesthesia, ICU admission and disease prognosis were compared between the two groups. Logistic regression model was used to analyze the risk factors of atelectasis after hepatectomy. Results Patients in the atelectasis group had higher mortality(5.1% vs. 0.5%, P=0.002), longer hospital stay [21(17, 29) d vs. 16(13, 21) d, P<0.001], longer endotracheal intubation time[8.0(4.0,16.0) h vs. 6.0(3.5,11.0) h, P=0.002], longer ICU stay [2(2, 5) d vs. 2(2, 2) d, P<0.001] and higher occurrence rate of hypoxemia(49.5% vs. 27.7%, P<0.001). Logistic regression analysis showed that longer operative time [odds ratio(OR)=1.005, P=0.001]and perioperative hypotension (OR=1.974, P=0.032) were independent risk factors for atelectasis in critically ill patients after hepatectomy. Conclusions The incidence of atelectasis is high after hepatectomy and patients with atelectasis after hepatectomy have higher rates of mortality, and longer hospital stays. Longer operative time and perioperative hypotension are independent risk factors for postoperative atelectasis.