Objective:To investigate the efficacy of free superficial circumflex iliac artery perforator flap (SCIAPF) in reconstruction of the donor site of hallux nail flap.Methods:From December 2015 to December 2022, Section Ⅲ of Department of Hand Surgery of Hangzhou Plastic Surgery Hospital conducted thumb reconstruction surgery with free hallax nail flaps for 12 patients with traumatic defects of thumbs. Six patients had degloving injuries of thumb with intact bone scaffold and extensor-flexor tendon. Among the other 6 patients with thumb defects, 3 had grade I defect, 2 had grade II defect and 1 had grade Ⅲ defect, according to Gu Yudong's classification. Free SCIAPFs were used to reconstruct the donor sites of hallux nail flaps. Sizes of the flaps were 3.0 cm× 6.5 cm-9.0 cm ×7.0 cm. All donor sites in the abdomen were directly sutured. After surgery, functional evaluations of the reconstructed thumb were conducted through follow-ups at outpatient clinics and(or) by WeChat interviews, according to the Evaluation Trial Standards of Upper Limb Partial Functional of Hand Surgery of Chinese Medical Association, and the functional evaluation of donor feet was conducted according to the Maryland foot function evaluation standard.Results:Successful survival of the 9 cases of flap in the donor site of hallux nail flap. One patient had venous occlusion of flap and survived after timely surgical exploration. One flap had partial necrosis at the tip of flap, and the wound was eliminated with local transfer of a flap. One patient had necrosis over most of the flap with the base of the flap survived, and the wound was repaired by a stage-II skin grafting. The donor sites at groin healed in stage-I in all of 11 patients with a linear scar. One patient who had haematoma at the donor site was cured by removal of the haematoma and a re-suture. All the patients received a 3 to 24 months of postoperative follow-up. According to the Evaluation Trial Standards of Upper Limb Partial Functional of Hand Surgery of Chinese Medical Association, 10 patients were in excellent and 2 in good. All of the great toes remained with original length and recovered normal flexion and extension. No patient suffered pain while walking and running. According to the Maryland foot function evaluation standard, 10 patients were in excellent and 2 in good. All SCIAPFs were satisfactory in colour and texture. Five patients had bloated flaps and underwent Hacks in the stage-Ⅱ.Conclusion:Application of a free SCIAPF in reconstruction of the donor site for hallux nail flap can effectively preserve the appearance and function of the donor site. Meanwhile, the scar in the donor site of groin is concealed with little damage, therefore the groin meets the requirements as a donor site of a flap.