Objective To evaluate the clinical results of flexor hallucis longus (FHL) tendon transfer in treatment of patients with Achilles tendon defects of more than 6 cm. Methods Between January 2005 to February 2009, 19 patients with Achilles tendon defects, 13 males and 6 females, were treated with FHL tendon transfer. Their ages ranged from 20 to 61 years, with an average of (42. 6 ± 8.2)years. Fifteen defects were found during tendonitis debridement, and 4 were old ruptures. Time from rupture to surgery ranged from 0 to 6 months (average, 2.6 months). Defects were 6 cm to 10 cm long. Procedures were performed in a two-incision manner. The postoperative ROM of ankle joint, American Orthopaedic Foot and Ankle Society(AOFAS) and visual analogue scale(VAS) scores were recorded at 3 months, 12 months,and the last follow-up. The results were statistically analyzed to evaluate the functional recovery. Results Follow-ups lasted from 12 to 48 months (average, 22. 2 months). At the last follow-up, the average ROM of ankle joint was 17.8°± 1.9° at dorsal flexion and 39.1°±2.3° at plantar flexion, and the last average AOFAS score was up to (91.8 ± 1.7), significantly different from those at 3 months after surgery (P＜0.05), but not significantly different from those at 12 months (P＞0.05). The difference were significant between the results of 3 months and 12 months (P＜0.05). The last average VAS score was (1.0±0.7),significantly different from those at 3 months and 12 months(P＜0.05) . There was also significant differences between the VAS scores of 3 months and 12 months (P＜0.05). Patient's satisfaction was 100%.Conclusion FHL tendon transfer is an efficient procedure for long Achilles tendon ruptures associated with tendonitis in relieving pain and maintaining the function of ankle joint.