Background Acute osteomyelitis has great harmfulness. To conduct comparative analysis on the difference of clinical effect of CT diagnosis and X-ray plain film diagnosis in children with acute osteomyelitis during emergency treatment, to provide guidance for the diagnosis and treatment of this disease. Methods The study subjects were 32 children with acute osteomyelitis. All the children were examined by X-ray and CT before surgery. Image characteristics and detection rates of bone destruction, changes in periosteum and cortex were compared. Funding X-ray scanning image: for the children with acute osteomyelitis in the early stage, the symptoms were demonstrated as that the submuscular space disappeared, and the boundary between subcutaneous and muscle tissues was blurred. CT scanning image: the images in early stage showed hyperemia and edema of soft tissue, with a slightly lower density of lesion, disappearance of interfascicular space, and a low-density abscess cavity in the center. The detection rate of bone destruction in CT scan was obviously higher than that in plain X-ray, in terms of bone destruction in special morphology, bone shell destruction in residual expansion, circular bone destruction, and peripheral bone defect, and the detection rate of periosteum and cortex changes was higher than that in plain X-ray, The diagnostic sensitivity and specificity of CT in children with acute osteomyelitis during emergency treatment were better than that of X-ray plain film. Interpretation CT scan has good diagnostic accuracy, sensitivity and specificity during emergency treatment of this disease.