Abstract:Objective To investigate the changes of cellular immunity in children suffered with Streptococcus Pneumoniae (SP) pneumonia, provid the reasonable suggestions of clinical targeted use of immune modulators Methods By using the method of flow cytometry instrument detection in January 2012 - February 2013 in our hospital at the records of 158 cases of pediatric SP infection in children with peripheral blood T cell subsets, B lymphocytes and NK cells were determined. An alternate period children to hospital to do physical examination of 40 cases of control group. Results Compared with the control group, the serum level of CD3+, CD4+, CD8+T lymphocytes and NK cells decreased significantly in SP infected children group, the ratio of CD4+/ CD8+ also decreased significantly. the serum level of CD19+B lymphcytes increased significantly,the differences were statistically significant (P < 0.01). Conclusion The humoral immune responses of SP infected pneumonia children were characterizsd by the increased serum level of B lymphocytes .it can be a helpful basis for the targeted clinical use of immune modulators.