Objective: To eludicate the risk factors of mechanical ventilation and prolonged mechanical ventilation in patients with severe multiple injuries. Methods: Consecutive patients with severe multiple injures who were treated in Peking University People’s Hospital Trauma Medical Center between December 2016 and December 2019 were enrolled in this restropective chart-review study. According to mechanical ventilation and ventilatory time, the patients were divided into mechanical ventilation (MV) group and non-mechanical ventilation (NMV) groups, prolonged mechanical ventilation (PMV) group and shortened mechanical ventilation (SMV) groups. Clinical data such as gender, age, base excess, mechanism of injury, Glasgow Coma Scale (GCS), abbreviated injury scale (AIS) and injury severity score (ISS) were collected. To indentify the risk factors of mechanical ventilation and prolonged mecha-nical ventilation, univariate and multivariate Logistic analyses were carried out. Results: In the present study, 112 patients (82 male, 30 female) with severe multiple injuries having a median age of 52 (range: 16-89 years) and a median ISS of 34 (range: 16-66) were enrolled. The primary mechanism of injury was traffic accident injury and falling injury. In the study, 62 and 50 patients were assigned to MV and NMV groups, respectively. Logistic analysis showed that GCS (OR=0.72, 95%CI: 0.53-0.92, P=0.03), base excess (OR=0.56, 95%CI: 0.37-0.88, P=0.002) and multiple rib fracture (OR=1.72, 95%CI: 1.60-2.80, P=0.012) were independent significant risk factors for mechanical ventilation after severe multiple injuries. Within the mechanical ventilation group, 38 and 24 patients were assigned to PMV and SMVgroups, respectively. Compared with the SMV group, the PMV group had a higher ISS and higher rate of severe head trauma. The length of hospital stay of PMV group was longer than that of SMV groups. Meanwhile, the incidence of tracheotomy in PMV group was high. Conclusion: GCS, base excess and rib fracture might be independent risk factors for mechanical ventilation. Higher ISS and lower GCS might prolong the ventilatory time and the length of hospital stay. Meanwhile, the incidence of tracheotomy was high in PMV group because of the longer ventilatory time and poor consciousness.