Objective To investigate the characteristics of the clinical application of ulnar artery flap in the repair of oral and maxillofacial soft tissue defects. Methods The clinical data of 12 patients with oral and maxillofacial defects repaired with ulnar artery flap between June 2021 and July 2023 was retrospectively analyzed. Among them, 11 cases were male and 1 case was female; their ages ranged from 28 to 76 years, with a mean age of 54.8 years. The lesions were located in the lateral margin of the tongue in 3 cases, the root of the tongue in 2 cases, the base of the tongue in 4 cases, and the buccal region, upper gingiva, and lower lip in 1 case each. The pathological types were squamous cell carcinoma in 11 cases and adenoid cystic carcinoma in 1 case; according to the TNM staging of the International Union Against Cancer (UICC), there were 5 cases of T3N0M0, 2 cases of T3N1M0, 1 case of T4aN0M0, 1 case of T4aN1M0, 1 case of T4aN2bM0, and 2 cases of T4aN2cM0. After complete resection of the lesion, the defect ranged from 6 cm×3 cm to 8 cm×5 cm. Preoperatively, colour Doppler ultrasound was used to detect the non-dominant forearm, measure the thickness of the subcutaneous fat in the donor area, confirm and mark the ulnar artery and reflux vein, and measure the diameter of the vessels, flow velocity, and the perforator position; intraoperatively, the flap was designed, prepared, anastomosed, and positioned according to the corresponding data. The vessels were all anastommosed with one artery and two veins to form a super-reflux. After complete hemostasis, the defects were repaired with sliding flap (2 cases), direct suture (4 cases), biomembrane (2 cases), or razor thin skin graft (4 cases). Results No vascular crisis occurred after operation, and all the flaps survived in 12 cases. Wounds in the donor site healed by first intention in 10 cases and by second intention in 2 cases. Wounds in the recipient site healed by first intention in all cases. All 12 patients were followed up 5-18 months, with an average of 11.4 months. The colour and texture of the flap were normal. The function of hand and upper limb was evaluated according to the trial standard of upper limb function assessment of the Chinese Society of Hand Surgery of the Chinese Medical Association, and the score was 65-81 (mean, 71.3), and achieved excellent in 1 case and good in 11 cases. The score of Oral Health Impact Scale (OHIP) was 9-18, with an average of 14.2, and the oral function was satisfactory. During the follow-up, 1 case had local recurrence and underwent extended resection again, while the other patients had no recurrence or metastasis. Conclusion For moderate soft tissue defects with complex oral and maxillofacial function, ulnar artery flap repair is effective.