Objective To investigate the index changes of the immune function of children respiratory tract infection. Methods The respiratory diseases children who hospitalized in Dalian Children's Hospital were divided into bronchitis group, pharyngitis group and pneumonia group. 40 normal children were choosed as control group. The three whole blood T lymphocyte differentiation antigen CD3, CD4, CD8 and ratio of CD4/CD8 were detected by using flow cytometry, and immunoglobulin (IgG, IgM, IgA), complement (C3, C4) in serum were detected by using nephelometry endpoint. Results The CD3, CD4, CD4/CD8 in bronchitis group, pharyngitis group and pneumonia group were lower than that of control group, while CD8 was higher than controls. The serum immunoglobulin and C3 level in three groups were lower than that of control group (p<0.05), but the C4 levels were basically the same compared with the control group without statistically significant. The cellular immune function and humoral immune function in children with ages 0-3 and 4-6 were lower than the control group, but without significant difference in 7-12 year old Children. There was no significant difference on respiratory tract infections with gender of children. Conclusion Respiratory diseases in children are immune dysfunction and disorder. The lower children ages are with the lower immune function and easier to cause respiratory diseases. Respiratory diseases in children are mainly under 6 years old and unrelated to gender.