Objective To evaluate the effectiveness of posterior malleolus fixation on the function of ankle in patients with ankle fracture. Methods Between June 2007 and June 2009, 110 patients with ankle fracture were treated with posteriormalleolus fixation in 59 patients (fixation group) or without fixation in 51 patients (non-fixation group). In fixation group, there were 31 males and 28 females with an average age of 62.6 years (range, 19-75 years); the causes of injury included traffic accident (20 cases), falling (18 cases), and sprain (21 cases) with a disease duration of 1-3 days (2.2 days on average); and the locations were left ankle in 32 cases and right ankle in 27 cases, including 6 cases of type I, 23 of type II, 19 of type III, and 11 of type IV according to the ankle fracture clssification. In non-fixation group, there were 38 males and 13 females with an average age of 64.5 years (range, 16-70 years); the causes of injury included traffic accident (15 cases), falling (12 cases), and sprain (24 cases) with a disease duration of 1-3 days (2.5 days on average); and the locations were left ankle in 22 cases and right ankle in 29 cases, including 8 cases of type I, 16 of type II, 19 of type III, and 8 of type IV according to the ankle fracture clssification. There was no significant difference in general data between 2 groups (P gt; 0.05). Results All patients of 2 groups achieved wound heal ing by first intention. The patients were followed up 12-18 months (16 months on average). X-ray films showed that fractures healed at 8-12 weeks (10 weeks on average) in fixation group and at 10-14 weeks (12 weeks on average) in non-fixation group. There were significant differences in the cl inical score (89.28 ± 8.62 vs. 86.88 ± 9.47, P lt; 0.05), postoperative reposition score (33.34 ± 2.15 vs. 31.24 ± 2.89, P lt; 0.05), and osteoarthritis score (13.22 ± 1.66 vs. 12.46 ± 2.03, P lt; 0.05) according to Phill i ps ankle scoring system between 2 groups at last follow-up. There was no significant difference in cl inical score of type I and II patients between 2 groups (P gt; 0.05), but significant differences were found in cl inical score and osteoarthritis score of type III and IV patients between 2 groups (P lt; 0.05). There were significant differences in the postoperative reposition score between 2 groups in all types of fractures (P lt; 0.05). Conclusion The posterior malleolus fixation may provide satisfactory cl inical functional outcomes for ankle fracture. Proper fracture classification and correct method of internal fixation are important for achieving good reduction and improving the long-term results.