Objective To investigate the application value of chest CT in identifying mycoplasma pneumonia (MP) infection and MP combined with streptococcus pneumonia (SP) infection in children. Methods A retrospective analysis was performed on the data of 83 children with MP in the hospital from June 2015 to June 2018. all of them underwent streptococcal blood culture and serum MP-Ig examination. According to the examination results, 40 children with MP were included in the MP group. 43 children with MP combined with SP were included in the MP-SP group. Both groups underwent chest CT examination, and the findings were analyzed. The incidence of lymph node shadow and pleural effusion, chest CT signs and incidence of lung lesions were compared between the two groups. Results The incidence of pleural effusion in MP group was significantly lower than that in MP-SP group (P<0.05). The mean transverse diameter of lymph node shadow and pleural effusion thickness of MP group were smaller than those of MP-SP group (P<0.05). The incidence rates of chest CT bronchial vascular bundle thickening, reticular shadow, ground glass shadow and bronchial wall thickening in MP group were significantly higher than those in MP-SP group (P<0.05). The incidence of lung lesions like irregular consolidation in the lung in MP group was lower than that in MPSP group while the incidence of fan-shaped thin shadow was higher than that in MPSP group (P<0.05). Conclusion Lung lesions in children with MP are mainly caused by interstitial lesions, while lung lesions in children with MP and SP are caused by alveolar inflammation, which is one of the criteria for identifying the two kinds of pneumonia.