Objective To explore the diagnostic value of multi-slice spiral CT (MSCT) in children with supracondylar fractures. Methods A total of 62 patients with supracondylar humerus fractures admitted and treated in our hospital from April 2017 to July 2017 were selected. All the 62 patients underwent image post-processing after CT scan, and the characteristics of CT scan and CT post-processing for supracondylar humerus fractures were analyzed, and the detection rate, sensitivity and specificity of CT scanning and CT post-processing were compared. Results The detection rate, sensitivity and specificity of CT post-treatment for supracondylar humerus fractures were 100%, 98.38% and 98.38%, respectively, significantly higher than 90.32%, 85.48%, and 87.09% of CT plain scan, with statistically significant difference (χ2 =6.305, 6.961, 5.871, P<0.05).In 54 patients, bone continuity was interrupted on the humeral condyle, with poor alignment of broken ends, and free small bone mass was observed around 36 patients. MIP images in the image visual display the line and the end of fracture shift condition, VR images can clearly show the rotating shift from multiple perspectives, 39 cases (62.90%) patients with fracture distal rotating about 30°, 23 cases (37.09%) patients with distal fracture 10°-15° rotation. Conclusion The multi-slice spiral CT post processing technique has high detection rate, sensitivity and specificity for the diagnosis of supracondylar humerus fractures in children.