Objective: To study the anatomic basis of the bi-pedicled V-Y gastrocnemius myocutaneous flap for repairing the composite Achilles tendon defect. Methods: The pedicle anatomy of the bi-pedicled V-Y gastrocnemius myocutaneous flap was examined on 30 cadaver specimens. The sliding distances of the flap were measured at different knee flexion degrees. The bi-pedicled V-Y gastrocnemius myocutaneous flap was applied in 12 cases of Achilles tendon defect with simultaneous skin and soft tissue defect. Results: The sural arteries could be classified into four types. After cutting off the gastrocnemius origin with a Z-shaped incision, the sliding distance of the flap reached (3.7±0.5)cm when the knee flexed 0°,(4.9±0.7)cm when the knee flexed 30°,(6.7±0.7)cm when the knee flexed 60°and (9.2±0.9)cm when the knee flexed 90°. All the defects healed. The patients recovered ambulation with satisfactory knee and ankle function.The follow-up was 4 months -12 years. Conclusions: Different sural artery types should be noticed during the harvest of the bi-pedicled V-Y gastrocnemius myocutaneous flap. With 90°knee flexion,this flap is suitable for one-stage repair of composite Achilles tendon defect within 9.2 cm±0.9 cm.