Abstract: Objective　To explore the changes of serum Clara cell secretory protein 16 (CC16), pulmonary surfactant protein D (SP-D) in children with pneumonia and its clinical significance. Methods　A total of 81 pediatric patients with community-acquired pneumonia were selected, including severe pneumonia with mechanical ventilation group (n=21), severe pneumonia with non-mechanical ventilation group (n=30), mild pneumonia group (n=30), and the control group (n=20) was selected in the physical examination of healthy children over the same period. We detected the concentration of serum CC16, TNF-α, IL-6 and SP-D for the 4 groups by ELISA, and evaluated the clinical values of serum CC16, TNF-α, IL-6 and SP-D for severe pneumonia by using ROC curve. We recorded pulmonary dynamic compliance (Cdyn), airway resistance (Raw), peak inspiratory pressure (PIP), work of breathing (WOB) and other respiratory mechanical parameters, and analyzed the correlations between CC16 and TNF-α, IL-6, SP-D and respiratory mechanical parameters. Results　The concentrations of serum CC16 in pneumonia group were all significantly lower than that in the control group, and those in severe pneumonia groups were lower than that in mild pneumonia group, and mechanical ventilation group was lower than that in non-mechanical ventilation; the concentration of serum TNF-α, IL-6 and SP-D in pneumonia groups were all obviously higher than that in the control group, and severe pneumonia group were higher than that in mild pneumonia group, and those in mechanical ventilation group were also higher than that in non-mechanical ventilation group (P<0.05). Compared to that before removing the ventilator, concentration of serum CC16 in severe pneumonia with mechanical ventilation group decreased significantly at 1 hour and lowered down at 72 hours; but the concentration of serum TNF-α, IL-6 and SP-D in severe pneumonia with mechanical ventilation increased significantly at 1 hour and went higher at 72 hours, the differences were all statistically significant (all of P<0.05); compared to  that before weaning from the ventilator, the value of Cdyn decreased obviously in severe pneumonia with mechanical ventilation at 72 hours and lowered down at 1 hour; but the values of Raw, PIP, WOB in severe pneumonia with mechanical ventilation increased obviously at 72 hours and more higher at 1 hour, the differences were all statistically significant (all of P<0.05). The concentration of serum CC16 showed all negative correlations with TNF-α, IL-6 and SP-D, but it showed positive correlation with Cdyn ( all of P<0.01). In the ROC curve, the area under the ROC curve of CC16, TNF-α, IL-6 and SP-D in serum was 0.905, 0.704, 0.832, 0.825, respectively (for all of which P<0.01). Conclusion　The concentrations of serum CC16 and SP-D were associated with the severity of community acquired-pneumonia in children. The level of serum CC16 was positive associated with Cdyn in children with mechanical ventilation. CC16 has better prediction and evaluation effect on the change of severe pneumonia.