[Objective] To compare the clinical efficacy of cannulated screw fixation versus support plate fixation of the posterior malle-olar fracture fragment in the trimalleolar fractures. [Methods] A retrospective study was done on 68 patients who received surgical treat-ment for trimalleolar fractures from February 2018 to February 2021. According to the surgeon-patient communication, 41 patients had theposterior malleolus fragment fixed with cannulated screws (CS), while the other 27 patients were fixed with support plates (SP). The data re-garding to perioperative period, follow-up and images were compared between the two groups. [Results] There were no significant differenc-es in terms of operation time, incision length, intraoperative blood loss, intraoperative fluoroscopy times, incision healing grade, hospitalstay, walking time, occurrences of incision infection and thrombosis events between the two groups (P＞0.05). However, the CS group provedsignificantly superior to the SP group in terms of incidence of toe flexion contracture [case (%), 2 (4.9) vs 7 (25.9), P=0.012] and implant irri-tation [case (%), 3 (7.3) vs 11 (40.7), P＜0.001]. Compared with those 3 months after surgery, the VAS score, AOFAS score and ankle-dorsi-flexion/plantar flexion ROM in both groups were significantly improved at the last follow-up (P＜0.05), whereas which were not statisticallysignificant at any corresponding time points between the two groups (P＞0.05). Radiographically, there were no statistically significant differ-ences in the quality of fracture reduction, bone healing and traumatic arthritis between the two groups (P＞0.05). The tibiofibular clear space(TFCS) and medial clear space (MCS) in both groups were significantly decreased at the last follow-up compared with those preoperatively(P＞0.05), while there were no significant differences in TFCS and MCS between the two groups at corresponding time points (P＞0.05).[Conclusion] Both cannulated screws and support plates do effectively fix posterior malleolus fracture, and achieve satisfactory clinical con-sequences, despite that the progression of post-traumatic arthritis needs to be furtherly followed up. Compared with support plate fixation,cannulated screw fixation is simpler and more effective, with fewer implant-related complications.