Objective To study common Gram negative bacterial pathogens and their drug resistant pattern in sputum isolates from patients in pediatric intensive care unit (PICU) of Chengdu children' s hospital. Methods Comparing to the period of 2004-2006 with 2007-2009, we retrospectively reviewed eligible sputum isolates of common Gram negative bacilli and their drug resistance pattern. All specimens were processed according to standard microbiological methods for both quantitative and qualitative cultures. Pathogen was the single predominant growth after two consecutive cultures. Strict quality control was used in all test agents and paper disk for drug resistance analysis. Results Total of 598 Gram negative bacterial isolates were identified in patients over 6 years. The first 5 bacteria respectively were Escherichia coli 167 samples(27.93%), Klebsiella pneumoniae 109 samples ( 18.23% ), Enterobacter cloacae 93 samples ( 15.55% ),Acinetobacter baumannii 64 samples ( 10. 7% ), Pseudomonas aeroginosa 43 samples (7. 19% ). They were mostly sensitive to Imipenam, Amikacin, Piperacillin/Tazobactam. Most drug resistance rate was found in Amoxicillin, Ampicillin, Cephalosporin. Apart from Pseudomonas aeroginosa and Acinetobacter Baumannii,no Gram negative bacteria was found to be resistant to Imipenam. Klebsiella pneumoniae and ESBL secreting Escherichia coli isolates were obviously increasing when compared to 3 years ago. Conclusion Comparing the period of 2004-2006, the Gram negative bacterial isolates were increasing in our PICU patients during 2007 to 2009. Close monitoring of drug resistance pattern changes in PICU would guide rational use of antibiotics in these critically ill children.