Objective To analyze the failure rate and failure factors related to ventilator weaning off in children. Methods Clinical data of 214 patients who received mechanical ventilation in pediatric intensive care unit of Tianjin Children's Hospital from Jan 2005 to Dec 2008 were analyzed retrospectively. Results There were 141 planned extubation events,122 of which were successful and 19 of which were unsuccessful.The failure rate of planned extubation was 13.5%. The failure rate of infants less than 6 months was higher than that of infants more than 6 months, but there was no significant difference ( 15.0% vs 9. 8%, P ＞0.05). The success rate of extubation in pneumonia cases (90. 7% )was higher than that in others (P ＜0. 05 ). The duration of mechanical ventilation had no effect on success rate of extubation ( (7. 64 ± 5.68 ) d vs (6. 95 ± 3. 14) d, P ＞ 0. 05 ). The duration of corticosteroid treatment after extubation in the successful group was less than that in the failure group ( ( 12. 35 ±9. 69) h vs ( 18.63 ± 12. 17) h,P ＜0. 05). According to the result of multiple linear regression analysis ( R2 = 0. 093), airway obstruction was the high risk factor of the extubation failure( F = 14. 256, P ＜ 0. 001 ). Conclusion Currently,weaning from mechanical ventilation in PICU depends on the combination of pediatricians' experience and objective indicators. The key point for improving the success rate of exubation is that we should explore reasonable and feasible extubation protocol and discover and exclude the related factors of exubation failure as earlier as possible.