ObjectiveTo summarize the relationship between preoperative duration of mechanical ventilation and prognosis in patients with ventricular septal defect. MethodsThe clinical data of patients with ventricular septal defect requiring ventilator support preoperatively and undergoing surgical treatment in our hospital from May 2009 to May 2020 were retrospectively reviewed. Based on the duration of preoperative ventilation, the patients were divided into three groups: a group A (0-47 hours), a group B (48-96 hours), and a group C (＞96 hours). Each group's postoperative recovery, complications, and medical costs were analyzed. Results Finally 272 patients were enrolled, including 154 males and 118 females, with a median surgical age of 2 (1, 4) months. There were 43 patients in the group A, 75 patients in the group B, and 154 patients in the group C. Early death occured in 3 (1.3%) patients, all in the group C. No statistical difference in mortality was found among the three groups (P=0.734). The mean postoperative duration of mechanical ventilation in the three groups was 158.6±133.5 hours, 101.2±56.1 hours, and 133.1±97.9 hours, respectively. The group B had significantly shorter duration than the other two groups (P＜0.05). The mean postoperative hospital stay in the three groups was 17.5±9.9 days, 13.5±5.8 days, and 16.5±10.8 days, respectively. Postoperative hospital stay in the group B was significantly shorter than that in the other two groups (P＜0.05). The mean total in-hospital cost in the three groups were 89 000±34 000 yuan, 87 000±21 000 yuan, and 109 000±41 000 yuan, respectively. The costs in the group C were significantly higher than those in the other two groups (P≤0.001). ConclusionPrompt surgical repair is necessary for patients with ventricular septal defects requiring ventilator support preoperatively. However, attention should be paid to surgical timing. Preoperative duration of mechanical ventilation is associated with better surgical outcomes within 48-96 hours than 0-47 hours or ＞96 hours.