Objective To analyze the clinical features of Mycoplasma pneumoniae necrotizing pneumonia (MPNP) and bacterial necrotizing pneumonia (BNP) and to observe the changes of inflammatory indicators. Methods The clinical data of 72 children diagnosed with MPNP or BNP from 2016 to 2021 were retrospectively analyzed. Results There were 43 children in MPNP group and 29 children in BNP group. The median age was 7.9 years in MPNP group and 1.9 years in BNP group (P<0.01). In the BNP group, the rates of shortness of breath, triple concave sign, and non-invasive ventilator use were 79.3%, 37.9%, and 51.7%, respectively, whereas in the MPNP group, the rates were 37.2%, 9.3%, and 18.6% (P<0.05). Streptococcus pneumoniae and Staphylococcus aureus were the predominant pathogens in the BNP group, making up 76% of all cases. The median C-reactive protein and procalcitonin levels in the BNP group within 3 days of disease course were 83 mg/L and 29.9 ng/mL respectively, which were higher than those in the MPNP group (14 mg/L and 0.1 ng/mL) (P<0.05). At days 4-7 and 8-14 of disease course, the median neutrophil ratio in MPNP group was 78.2% and 80.4%, while that in BNP group was 65.8% and 59.8% (P<0.05). There was no significant difference in the total number of white blood cells between the two groups at days 1-3 of disease course (P>0.05). The median blood D-dimer concentration in the MPNP group was 4.1 mg/L, which was higher than that in the BNP group (3 mg/L) (P<0.05). The pleural fluid leukocytes in MPNP group were mainly mononuclear cells, while those in the BNP group were mainly multinucleated cells. The glucose level of pleural fluid in BNP group was (2±2) mmol/L, which was significantly lower than that in the MPNP group [(6±2) mmol/L, P<0.01)]. The time of pulmonary cavity necrosis in MPNP group was (23.4±10.0) days, while that in BNP group was (10.4±5.7) days (P<0.01). In MPNP group, pulmonary embolism was observed in 8 cases, bronchoscopic plastic formation was observed in 7 cases, and sequelae (lumen stenosis and occlusion) were observed in 21 cases. Pyopneumothorax occurred in 12 cases of BNP group. Conclusions In BNP group, C-reactive protein and procalcitonin increased significantly at days 1-3 of disease course. The children in BNP group were prone to dyspnea and pyopneumothorax. In MPNP group, the proportion of neutrophil increased significantly after 4 days of disease course, the level of D-dimer in blood was higher, the occurrence of pulmonary cavity necrosis was late, and pulmonary embolism was easy to occur, and the plastic formation could be seen under bronchoscopy, and the incidence of sequelae of lumen stenosis and occlusion was high.