Renal autotransplantation (RA) offers significant technical advantages for the management of certain complex renal vascular diseases, such as complex renal aneurysms and renal artery malformations. This report describes a case of a 5-year-old child with a complex left renal artery aneurysm combined with multiple aneurysms. The child was admitted to Peking University People's Hospital in December 2023 due to a one-year history of intermittent abdominal pain, with an abdominal mass detected in the past month. Computed tomography angiography(CTA) revealed multiple vascular anomalies, including: (1) a left renal artery aneurysm, (2) an abdominal aortic aneurysm, and (3) a right iliac artery aneurysm. After a comprehensive evaluation of these findings, the surgical team developed a treatment plan that involved the excision of the left renal artery aneurysm, autotransplantation of the left kidney, and resection of the abdominal aortic aneurysm with an artificial vascular catheterization. During surgery, it was discovered that the left renal artery anatomy was highly complex. The artery had two primary branches, along with an additional polar artery located at the lower pole. The aneurysm was identified at the distal end of the renal artery trunk, with a pronounced bulging at the intersection between the main renal artery trunk and its secondary branches. Due to these structural complexities, the team decided to use an ex vivo surgical approach to repair the aneurysm. Ex vivo repair involves temporarily removing the kidney from the body to repair the renal artery aneurysm with enhanced precision, enabling the surgical team to meticulously reconstruct the complex vascular architecture without the constraints of in vivo manipulation. The ex vivo repair of the renal artery aneurysm was successful, allowing for accurate vascular reconstruction and avoiding potential intraoperative complications. Following the reconstruction, the kidney was autotransplanted back into the child's body, and blood flow was effectively restored to the organ. The therapeutic outcome was excellent, with the child experiencing no postoperative complications. The patient recovered well and was discharged from the hospital in stable condition. This case underscores the value of renal autotransplantation combined with ex vivo repair for pediatric patients with complicated renal artery aneurysms. Through this report, we aim to provide insights and considerations for the surgical treatment of similar cases in children with complex renal vascular anatomy.