Abstract： Objective To investigate the common pathogenic bacteria distribution and drug resistance in children with lower respiratory tract infection,which guide how to use antibiotics and decrease the progress of drug resistance.Methods Nine hundred and ninety-seven cases of lower respiartory tract infection were analyzed retrospectively in the Department of Pediatrics of the First Hospital of Lanzhou University from Jan.2008to Dec.2010.The sputum samples were collected for routine bacterial cultivation.The antibiotic sentivity test were used for pathgen.Results The phelm cultivition amount is 997,bred and separated 498 bacteria of 425samples,the check rate is 42.73％.There were 151 Gram Positive Bacteria,which had a rate of 30.32％,and 321 Gram Negative Bacteria,which had a rate of 64.46％,and 26 fungi whose rate is 5.62％.The main bacteria was changed during the three years.There were significant differences in detection rate of pseudomonas aeruginosa(PA) and haemophilus parainfluenzae(HPI) during the three years.PA was declining while HPI was rising.There were no significant differences in detection rate of streptococcus pneumoniae( SP),staphylococcus aureus ( SA),escherichia coli( E.coli ),klebsiella pneumoniae ( K.pn ),haemophilus influenzae ( HI ) and fungi.There were no significant differences in detection rate of PA between different age groups.With the increasing of age,the detection rate of SP,HI and HPI trended to rise,whereas the detection rate of SA,E.coli and K.pn trended todecline.The resistance phenotype of SA,E.coli and HPI in detection rate had significant difference in each year.SP and SA were most sensitive to linezolid and vancomycin.Ecoli and K.pn were most sensitive to carbapenems.HI and HPI were relatively sensitive to common antibiotics.Conclution In the past three years,the main pathogen in children with lower respiartory tract infection were Gram Negative Bacteria.Among the bacteria,SP and Ecoli was the most,followed by SA,HI,K.pn,and HPI.These bacteria had signifeicant difference in dectection rate between different age groups.SP and SA were most sensitive to vancomnycin and linezolid.E.coli and K.pn were most sensitive to carbapenems.HI and HPI were relatively sensitive to common antibiotics.So clinical doctors should use antibiotics based on the microorganism cultivation and sensitivity test m order to decrease the drugresistance strain.