Abstract： Objective To analyze the clinical characteristics and prognosis of acute pyelonephritis (APN) in children.Methods A retrospective analysis was performed in 230 pediatric patients with APN admitted from January 2009 to December 2010.The clinical characteristics,etiology,drug-resistant and prognosis were reviewed,and logistic regression analysis was performed to identify the risk factors of renal scarring after APN.Results Among 230 patients with APN,93 were boys and 137 were girls with a malefemale ratio of 1∶ 1.47.Ninety-nine patients were younger than 1 year with a male-female ratio of 1.30∶1 ;75 patients were 1 to 5 year with a male-female ratioof 1 ∶ 2.75 ; 56 patients were older than 5 year with a male-female ratio of 1∶2.29.A total of 106 strains were detected,in which 91 strains were Gram-negative bacteria,13 strains were Gram-positive bacteria and 2 strains were fungus.The most frequent bacteria were Escherichia coli (65 strains,61.32％),Klebsiella pneumonia (13 strains,12.6％) and Enterococcus faecium (9 strains,8.49％).Forty-four strains of Escherichia coli produced ESBLs,and all of them were resistant to ampicillin,part of them resistant to cephalosporin,compound sulfamethoxazole and aztreonam,but all were sensitive to amikacin,amoxicillin/clavulanic acid,nitrofurantoin,and imipenem.Renal emission computed tomography (ECT) was performed again in 52 children who were followed up for 6-12 months,in which 31 cases (59.62％) developed renal scar,and 21 cases (40.38％) were recovered.Abnormalities in urinary system or vesicoureteric reflux were identified as the risk factors for renal scarring after APN (OR =6.89,P ＜ 0.05).Conclusions The incidence of APN in children drops with age,which is frequently in the males younger than 1 year,and in the females older than 1 year.Escherichia coli is the most frequent pathogen of APN in children,and most strains are multidrug resistant.Children with abnormalities in urinary system or vesicoureteric reflux are prone to develop renal scarring.