Primitive neuroectodermal tumours are clinically rare. Here, we report a case of a large peripheral primitive neuroectodermal tumour of the abdominal wall. The defect was reconstructed with the longest lateral circumflex femoral artery musculocutaneous flap reported to date. A 15-year-old male suffered rupture and bleeding of an abdominal wall mass with a volume of approximately 23*18*10 cm3, involving the whole layer of the abdominal wall. Pathological examination revealed a peripheral primitive neuroectodermal tumour. The tumour was removed via oncologic resection, and the abdominal wall was reconstructed with a bilateral 44*8 cm2 lateral circumflex femoral artery musculocutaneous flap combined with a titanium polypropylene patch. The patient had smooth recovery postoperative, and the functions of the donor and recipient areas of the flap were not significantly affected. In this case report, we describe a rare primitive neuroectodermal tumour of the abdominal wall, which invaded almost the entire abdominal wall due to delay of treatment. After thoroughly removing the tumour, we immediately reconstructed the abdominal wall with an ultra-long lateral circumflex femoral artery musculocutaneous flap and achieved better appearance and function after the operation. This case suggests that we should adopt an integrated scheme of surgery combined with radiotherapy and chemotherapy in the treatment of peripheral primitive neuroectodermal tumours. Under the premise of determining the blood supply, the lateral circumflex femoral artery musculocutaneous flap can be cut to a sufficient length.