Objective To investigate the application of anterior serratus branch of thoracodorsal vessel in repairing chest wall defect. Methods Between October 2018 and March 2021, bilateral free lower abdominal flaps were used to repair large-area complex defects after chest wall tumor surgery in 23 patients. The patients were all female; the age ranged from 23 to 71 years, with an average age of 48.5 years. There were 11 cases of locally advanced breast cancer, 4 cases of phyllodes cell sarcoma, 3 cases of soft tissue sarcoma, 3 cases of recurrence of breast cancer, and 2 case of osteoradionecrosis. The size of secondary chest wall defect after tumor resection and wound debridement ranged from 20 cm×10 cm to 38 cm×14 cm, the size of flap ranged from 25 cm×12 cm to 38 cm×15 cm, the length of vascular pedicle was 9-12 cm (mean, 11.4 cm). Fourteen cases of simple soft tissue defects were repaired by flap transplantation; 5 cases of rib defects (<3 ribs) and soft tissue defects were repaired by simple mesh combined with flap transplantation; and 4 cases of full-thickness chest wall defect with large-scale rib defect (>3 ribs) were repaired by “mesh plus bone cement” rigid internal fixation combined with flap transplantation. The anterior serratus branch of thoracodorsal vessel was selected as the recipient vessel in all cases, the revascularization methods include 3 types: the proximal end of the anterior serratus branch plus other recipient vessels (13 cases), proximal and distal ends of anterior serratus branch (6 cases), and proximal ends of two anterior serratus branches (4 cases). ResultsThe main trunk of thoracodorsal vessels was preserved completely in 23 patients. All patients were followed up 10-18 months, with an average of 13.9 months. After operation, the flap survived completely, the shape of reconstructed chest wall was good, the texture was satisfactory, and there was no flap contracture deformation. There was only a linear scar left in the flap donor site, and the abdominal wall function was not significantly affected. There was no tumor recurrence during follow-up. Conclusion The anterior serratus branch of thoracodorsal vessel has a constant anatomy and causes little damage to the recipient site, so it can provide reliable blood supply for free flap transplantation.