Objective To analyze the five years change of bacterial infection adn drug resistance in PICU and to provide evidence for use of na tibiotics rationally.Methods Al the pathoeg nic bacteria from patients in PICU of our hospital from January 1 2009 to Deec mber 31 2013 were analyzed retrospectiev ly. T hey were divided into five subgroups according to differetn years.Pathogenic batc eria and drug resistance in different years wre e collected na d the changes of such bacterial infection and drug resistance were compared and summarized.Results A total of 2 201 pathogenic bacterial strains were isolated from 14 361 specimens of five-year patients in PICU.The rate of gram negative bacteria in 2009 to 2013 were 83.2%,71.0%, 59.8%,58.9%, 52.5% respe ctively.The rate of gram positive bacteria in 2009 to 2013 were 16.8%, 29.0%,40.2%, 41.1%, 47.5% respectively.Top five pathogenic bacteria were staphylocco cus aureus (16.6%,366 strains),Escherichia coli (16.2%,357 strains),klebsiella pnue moniae (15.2%,334 strains), streptococ us pneumoniae (9.2%,202 strains),haemophilus influenzae (6.8%,149 strains).The infection rate of staphylococcus aureus increased year by year(6.4% to 27.0%).Drug sensitivity tets indicated that the rate of extended-spectrum beta-lactamases ( ESBL) positive escherichia coli and klebsiella pneumoniae were 28.3%and 38.3%,respectivle y.The rate of methicillin-resistant staphylococcus aureus ( MRSA) was 26.0%.Based on non-meningitis criterion,rate of penicillin resistance streptococcus pneumonia and multiple-drugresistance streptococcus pneumonia was 19.3%and 58.9%,respectively.There were no obvious changes in resistance rate of above-mentioned bacteria during the recent five years.Conclusion In the recent five years,gram negative bacteria is still the prevalent strain in PICU of our hospital,however the rate of gram positive bacteria increases year by year and staphylococcus aureus has become one of the five most common bacteria.The rate of ESBL positive escherichia coli,ESBL positive klebsiella pneumonia and MRSA has no obvious changes.Analysis of pathogenic bacteria and drug-resistance surveillance are of vital importance to guide treatments for critically ill patients and reduce drug-resistant bacterial strains.