Abstract: Objective　To explore the serum expression levels of Clara cell secretory protein (CCSP) and interleukin17 (IL-17) in children with Mycoplasma pneumoniae pneumonia (MPP) and its clinical significance. Methods A total of 72 children with MPP admitted to our hospital from May 2013 to November 2013 were enrolled including 38 cases in acute phase (20 severe cases, 18 mild cases) and 34 cases in recovery phase (18 severe cases, 16 mild cases). Meanwhile, 22 healthy children were selected as normal controls. The serum levels of CCSP and IL-17 were measured by ELISA. Results In acute phase of MPP, serum levels of CCSP decreased while IL-17 levels elevated compared with convalescent MPP children and healthy controls, the differences were statistically significant (P<0.05). There were no significant differences in serum levels of CCSP and IL-17 between convalescent MPP children and healthy controls (P>0.05). The level of CCSP were negatively correlated with IL-17 in acute phase of MPP (r=-0.75, P<0.05), but this correlation disappeared in recovery phase. In the acute phase of MPP, compared with mild cases, lower serum level of CCSP and higher level of IL-17 were observed in severe cases, and the differences were statistically significant (P<0.05). In recovery phase of MPP, no difference in level of either CCSP or IL-17 was found between severe cases and mild cases (P>0.05). Conclusions Both CCSP and IL-17 are involved in the pathogenesis and development of MPP, and also related to the severity of illness.