Abstract: OBJECTIVE To study the characteristics of children with lower respiratory infection, so as to provide reference for clinical treatment of children's lower respiratory infections. METHODS A total of 180 cases of children with lower respiratory infections hospitalized from Dec. 2014 to Dec. 2015 were chosen. Using the random method according to patients age group, who were divided into 86 cases baby group(< 1 year old), 55 cases in infants group (1 to 3 years old) and 39 cases in children series (> 3 years old). Atypical pathogens of lower respiratory tract and antinuclear antibody of the virus were detected by IFA, and the pathogen distribution, genders of children, age were compared. RESULTS The distribution rates of atypical pneumonia in baby and infant group were 5.81% and 12.73%, which were significantly lower than that in child group 51.28%(P<0.05). There were 45 children with antibody of respiratory tract positive and positive rate was 25.00%, 35 cases of children had the antibody of mycoplasma pneumoniae positive, and positive rate was 19.44%, 15 cases had other bacterial infection combined with mycoplasma pneumoniae and positive rate was 8.33%. The positive rates of mycoplasma pneumoniae and influenza B virus in child group were significantly higher than baby and infant group(P<0.05). There is no difference between different genders and positive rate of virus. CONCLUSION Respiratory syncytial virus is the main reason for the children's lower respiratory infection. The children more than 3 years old are mainly infected by mycoplasma pneumoniae. IFA is a quick, easy, high sensitive, strong specialist and good repeating use way of test, which should be used as a index for early detection of low respiratory infection in children.