Objective To explore the feasibility and effectiveness of mixed reality technology for localizing perforator vessels in the repair of mandibular defects using free fibular flap. Methods Between June 2020 and June 2023, 12 patients with mandibular defects were repaired with free fibular flap. There were 8 males and 4 females, with an average age of 61 years (range, 35-78 years). There were 9 cases of ameloblastomas and 3 cases of squamous cell carcinomas involving the mandible. The disease duration ranged from 15 days to 2 years (median, 14.2 months). The length of mandibular defects ranged from 5 to 14 cm (mean, 8.5 cm). The area of soft tissue defects ranged from 5 cm×4 cm to 8 cm×6 cm. Preoperative enhanced CT scans of the maxillofacial region and CT angiography of the lower limbs were performed, and the data was used to create three-dimensional models of the mandible and lower limb perforator vessels. During operation, the mixed reality technology was used to overlay the three-dimensional model of perforator vessels onto the body surface for harvesting the free fibular flap. The length of the fibula harvested ranged from 6 to 15 cm, with a mean of 9.5 cm; the size of the flap ranged from 6 cm×5 cm to 10 cm×8 cm. The donor sites were sutured directly in 7 cases and repaired with free skin grafting in 5 cases. Results Thirty perforator vessels were located by mixed reality technology before operation, with an average of 2.5 vessels per case; the distance between the exit point of the perforator vessels located before operation and the actual exit point ranged from 1 to 4 mm, with a mean of 2.8 mm. All fibular flaps survived; 1 case had necrosis at the distal end of flap, which healed after dressing changes. One donor site had infection, which healed after anti-inflammatory dressing changes; the remaining incisions healed by first intention, and the grafts survived smoothly. All patients were followed up 8-36 months (median, 21 months). The repaired facial appearance was satisfactory, with no flap swelling. Among the patients underwent postoperative radiotherapy, 2 patients had normal bone healing and 1 had delayed healing at 6 months. Conclusion In free fibular flap reconstruction of mandibular defects, the use of mixed reality technology for perforator vessel localization can achieve three-dimensional visualization, simplify surgical procedures, and reduce errors.