Pneumonia is a major threat to the health of children. Mycoplasma pneumoniae infection is a core cause of pediatric pneumonia, and the incidence of severe mycoplasma pneumoniae pneumonia (SMPP) has increased in recent years. SMPP leads to a range of extrapulmonary symptoms, including myocardial and liver injury, which may be life-threatening. Therefore, there is an urgent need to establish an early warning model for SMPP to improve the prognosis of pediatric pneumonia. This observational study aims to establish a early prediction model of SMPP. Development cohorts are enrolled from Beijing Friendship Hospital between 2018-1-1 to 2024-5-31, and validation cohorts are enrolled between 2024-6-1 to 2025-6-30.