Objective To investigate the value of multi-slice spiral CT (MSCT) in the differential diagnosis of posterior malleolus and posterior Pilon fractures. Methods CT imaging data of 100 cases of patients with distal posterior tibial fractures (including 38 cases of posterior malleolus fractures and 62 cases of posterior Pilon fractures) who were treated from January 2015 to May 2017 were retrospectively analyzed. Results The β angle, FAR1 and FAR2 of posterior malleolus fractures were significantly smaller or lower than those of Pilon fractures [(74.28±12.00) degrees, (6.81±3.29) %, (15.08±5.13)% vs (79.42±10.83) degrees, (23.79±12.34)%, (28.27±10.64)%] (P<0.05). The FAR1 and FAR2 of type I posterior malleolus fractures were significantly higher than those of type II (P<0.05). FAR1 of type II and type III were significantly larger than that of type I (P<0.05), but there was no significant difference between type II and type III (P>0.05). There was no significant difference in FAR2 between different types of posterior Pilon fractures (P>0.05). Conclusion Compared with the posterior malleolus fractures, the vertical correlation between sagittal plane and ground surface of posterior Pilon fractures is more obvious, the transverse and sagittal areas are significantly larger, and the risk of ankle joint dislocation is significantly higher.