Objectives The anterolateral thigh (ALT) flap is a versatile workhorse flap for the reconstruction of head and neck defects; however, variations in the location of perforators are a significant concern. This prospective study proposes a rapid, effective, and convenient method for mapping the location of sizeable perforators on the curved thigh skin surface using the visual coordinate system in computed tomographic angiography (CTA) images. Methods Fourteen patients suffering from defects after head and neck carcinoma resection underwent CTA prior to ALT flap reconstruction at the Department of Otolaryngology-Head and Neck Surgery, Beijing Friendship Hospital, Capital Medical University, from January 2018 to August 2021. Using sterile gauze swab developing lines pasted on the patients' thighs, we established a coordinate system visualized both in CTA images and the thighs. The perforator information was then compared between the CTA and intraoperative findings. Results Twenty-one perforators were detected on CTA in the designed flaps, which were also confirmed during the operation with a visual pulse. The course and source of the perforators were consistent with the intraoperative findings. The distances of perforator coordinate points between CTA and intraoperative findings were <5 mm. Another five perforators (mostly without visual pulse) found intraoperatively could not be identified on preoperative CTA. Most flaps survived in their entirety, and one flap suffered a small area of necrosis due to perforator compression. Conclusion This study demonstrated the efficacy of a novel perforator mapping method for anterolateral thigh flaps.