Abstract: During a year the authors collected 372 hospitalized and 86 healthy children and detected them for antibodies to Legionella with sonicated and EDTA antigens of 9 species(15 serogroups).The positive rate was 13.17%(49/372)in hospitalized children and 2.33%(2/86) in healthy children.95%CI was 9.73～16.61% and 0～5.52%, respectively.The significante variation was found in two kinds of people.372 patients were divided into 9 different diseases groups.The positive rate 40% in upper respiratory infection group was hightest.Nest was 33.33% in kidney or blood diseases group, 24.33% in neural system diseases group, 21.05% in unidentified fever group, 10.34% in congenital heart diseases group, 9.40% in pneumonia and 2.50% in bronchitis, respectively.The patients with Legionella inf ection were not found in other congenital diseases and surgical diseases group.The difference in the positive rates was significant in several groups.Hospitalized children infected most commonly by Legionella pneumophila(Lp), Tatlockia micdadei(Lm)and Fluoribacter bozemanae(Lb).The infeced patients in pneumonia group and congenital heart diseases mainly caused by Lp and Lm, however, in other groups Lm is commom to most diseases in children and different species or serogroups of Legionella may be of different pathogenic significance.