Abstract: 　Objective　To detect the clinical significance of high sensitive C-reactive Protein (Hs- CRP) and immune function in children with mycoplasma pneumoniae pneumonia (MPP). Methods 103 children with MPP, 47 cases of systemic inflammatory resPonse syndrome (SIRS group), 56 cases of non- systemic inflammatory resPonse syndrome (non-SIRS group) were recruited. 26 healthy children served as the control grouP. ELISA was used to detect the level of serum Hs- CRP, immune indexes, IgG, IgA, and IgM, Cellular immune CD3⁺, CD4⁺, CD8⁺, CD4⁺/CD8⁺. Results The level of serum Hs- CRP、IgG、IgM and CD8⁺ in control grouP were significantly lower than those in non-SIRS group and SIRS group (P<0.05). The level of IgA、CD3⁺,CD4⁺, CD4⁺/CD8⁺in control grouP were significantly higher than those in non-SIRS grouP and SIRS group (P<0.05). The level of serum Hs- CRP、IgG in SIRS group were significantly higher than those in non-SIRS group (P<0.05). The level of IgA、CD3⁺、CD4⁺、CD4⁺/CD8⁺ in SIRS grouP were significantly lower than those in non-SIRS group. There was no significant difference in non-SIRS group and SIRS group of IgM and CD8+（P>0.05）. The level change of serum hs-CRP were positively related with IgG (r=0.66， P=0.001) and were negatively related with IgA、CD4⁺、CD4⁺/CD8⁺ (r= 0.79, 0.67, 0.82, P all were< 0.05) in children with MPP. Conclusion Children with MPP have Immunity function（ including humoral immunity and cellular immunity ）disorder which is related to the disease status. The level of Hs - CRP could be an anpation index for the severity and immune function of the children with MPP.