Abstract: Objective To investigate the correlation between serum interleukin-18 (IL-18), interleukin-33 (IL-33) and expiratory nitric oxide (FeNO) in children with mycoplasma pneumonia. Methods Altogether 87 children with mycoplasma pneumonia admitted to our hospital from January 2017 to July 2018 was selected as observation group, and 90 children who underwent physical examination in Hospital from January 2017 to July 2018 were selected as the control group. The expiratory velocities of 25% vital capacity (FEF25%), 50% vital capacity (FEF50%), 75% vital capacity (FEF75%), forced vital capacity (FVC) and 1 second forced expiratory volume (FEV1) were measured by pulmonary function instrument; all subjects were collected peripheral venous blood on the 2nd day of admission, and serum was separated. Serum levels of IL-18 and IL-33 were determined by ELISA; and FeNO was detected by electrochemical method. The changes of pulmonary function, serum levels of IL-18 and IL-33 and FeNO in the two groups were compared, and the correlation between FeNO and IL-18 and IL-33 was analyzed. Results FEF 25%, FEF 50%, FEF 75%, FVC and FEV1 in the observation group were lower than those in the control group (all P<0.05). the serum levels of IL-18 and IL-33 the observation group were higher control group (P<0.05). FeNO value in the observation group was higher than that in the control group (all P<0.05). FeNO was positively correlated with IL-18 and IL-33. Conclusion Serum levels of IL-18, IL-33 and FeNO in children with mycoplasma pneumonia are increased, and there is a linear positive correlation between FeNO and IL-18 and IL-33, which is worthy of clinical reference.