Objective To explore the predictive value of bedside lung ultrasound score on the outcome of liberation from mechanical ventilation in critically ill children. Methods The children who received mechanical ventilation in the intensive care unit (ICU) from January to December 2019 were studied. The bedside lung ultrasound score (LUS) was performed before extubation, and the rapid shallow breathing index (RSBI) and oxygenation index (P/F) were collected simultaneously. The outcome of liberation was followed up. The receiver operating characteristic curve (ROC) and area under curve (AUC) were used to evaluate the predictive value of LUS score for the outcomes. Results In 106 children ( 62 boys and 44 girls) with median age of 9 ( 3 ~ 36 ) months, 97 cases ( 91 . 5 %) were successful and 9 cases ( 8 . 5 %) failed. Compared with the successful group, the PICU stay and catheterization time were longer, the severity score was lower, the LUS and RSBI were higher and the oxygenation index (P/F) was lower (all P< 0. 05 ) in the failure group. LUS score ≥ 16 was the best cut-off value for predicting liberation failure (AUC= 0 . 991 , sensitivity 88 . 9%, specificity 97 . 9%, P< 0 . 01 ), and the predictive efficacy was significantly better than P/F value and RSBI value (P< 0 . 05 ). Conclusions? Bedside LUS can effectively assist in evaluating the readiness of liberation from mechanical ventilation, and has a high predictive value for liberation outcome.