Objective To investigate the effectiveness of the lower abdominal conjoined flap with bilateral superficial inferior epigastric arteries (SIEA) for repairing the large soft tissue defects on the foot and ankle. Methods The clinical data of 18 patients with large soft tissue defects on foot and ankle treated between October 2017 and January 2020 were retrospectively analyzed, including 12 males and 6 females; the age ranged from 25 to 62 years, with a median age of 35 years. The causes of injury included machine injury in 9 cases, traffic accident injury in 5 cases, cutting injury in 2 cases, and electric injury in 2 cases. All wounds were accompanied by exposure of blood vessels, tendons, bones, and joints. Wound located at ankle in 8 cases, dorsum of foot in 6 cases, and sole in 4 cases. In the emergency department, complete debridement (the defect area after debridement was 15 cm×10 cm to 25 cm×16 cm) and vacuum sealing drainage on the wound was performed. The time from debridement to flap repair was 3-10 days, with an average of 5 days. According to the defect location and scope, the lower abdominal conjoined flap with bilateral SIEA was prepared. The size of the flap ranged from 15 cm×10 cm to 25 cm×16 cm. The length of vascular pedicle was 4.5-7.5 cm, with an average of 6.0 cm; the thickness of the flap was 0.5-1.2 cm, with an average of 0.8 cm. The abdominal donor site was closed in one-stage. Results One flap was altered as the conjoined flap with the bilateral superficial circumflex iliac artery because of the absence of the SIEA in one side. Except for 1 case of skin flap with distal necrosis, the flap healed after two-stage skin grafting repair; the rest skin flaps survived, and the wounds of the donor and recipient sites all healed by first intention. All patients were followed up 12-28 months, with an average of 16 months. The skin flap had a satisfactory appearance and soft texture, without abnormal hair growth or obvious pigmentation. Only linear scars were left at the donor site, and no complication such as abdominal hernia occurred. The foot and ankle function was satisfactory. At last follow-up, the American Orthopaedic Foot and Ankle Society (AOFAS) scores were rated as excellent in 16 cases and good in 2 cases. Conclusion The lower abdominal conjoined flap with bilateral SIEA is an ideal flap for repairing large defects of foot and ankle with less morbidity scarcely, which ascribed to its ease of dissection, adjustable thinness, and concealed donor site, as well as the flexible perforator match.