Purpose: With the development of microsurgical techniques, the anterolateral thigh (ALT) flap has been widely used in reconstruction of various soft-tissue defects. However, there were few studies focusing on the closure of the ALT flap donor site, especially when the width of the harvested ALT flap was more than 6 cm. The purpose of this study was to share our experience of using Keystone Design Perforator Island Flap (KDPIF) to repair the ALT flap donor site where can’t be closed without a skin graft.Method: A retrospective study was used to analyze 12 patients who underwent the reconstruction of the ALT flap donor site using KDPIF from February 2018 to December 2020. Demographics, flap characteristics, surgical technique, postoperative complications, Vancouver Scar Scale (VSS) score, and Scar Cosmesis Assessment and Rating (SCAR) score were statistically analyzed.Results: 12 patients (10 males, 2 females) with the mean age 47.5 years (range, 27-66 years) were included in this study. All ALT flap donor sites were closed by the KDPIF. The mean size of the harvested ALT flap (the donor site size) was 8.1 cm × 14.4 cm (range from 8.0 cm × 11.0 cm to 9.0 cm × 21.0 cm), and the mean size of keystone flap was 9.1 cm × 16.4 cm (range from 8.0 cm × 13.0 cm to 12.0 cm × 19.0 cm). At the mean follow-up of 8.3 months (range, 6-12 months), two patients suffered from the skin infection around the flap, which was controlled under the treatment of wound dressing change and oral antibiotics. Wound dehiscence, osteofascial compartment syndrome (OCS), venous return disorder, and skin necrosis were not presented in any patients. All patients were evaluated at the final follow-up with ASS core (mean, 6.7; range, 5-8) and SCAR core (mean, 7.3; range, 6-9).Conclusion: This study demonstrated that the KDPIF that can be used to close the ALT flap donor site primarily is an effective and alternative treatment for patients with a the width of the donor site more than 6 cm including the advantages of high survival rate, low morbidity, good aesthetics, and simple operation.