Objective To study the clinical efficacy of adjuvant therapy with glucocorticoids in children with lobar pneumonia caused by Mycoplasma pneumoniae. Methods One hundred and eight children with lobar pneumonia caused by Mycoplasma pneumoniae were randomly divided into routine treatment and hormone treatment groups. Both groups were treated with azithromycin and other symptomatic therapies. In addition to the basic treatment, the hormone treatment group was given dexamethasone 0.25-0.3 mg/(kg·d) by intravenous drip until the body temperature was normal. Then given oral prednisone tablets 0.5-1 mg/(kg·d) (gradually reduced) for a total treatment course of 7-10 days. Before and after treatment pulmonary functions were examined, and serum C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), interleukin-2 (IL-2) and interleukin-6 (IL-6) were measured. Results The duration of fever, cough relief time and pulmonary shadow absorption time on chest X-ray were significantly shorter in the hormone treatment group than in the routine treatment group (P<0.05). After treatment, the two groups showed improvements in serum CRP, ESR, IL-2, and IL-6 (P<0.05), but the hormone treatment group showed significantly more improvement (P<0.05). Varying degrees of mixed ventilation dysfunction were seen in the two groups before treatment, and hormone therapy significantly improved pulmonary function, especially promoting the recovery of small airway function. Conclusions Adjuvant therapy with glucocorticoids can effectively alleviate clinical symptoms, promote the absorption of pulmonary inflammation, and improve pulmonary function in children with lobar pneumonia caused by Mycoplasma pneumoniae.