Case presentation: The patient was a 62-year-old male with a left renal tumor with inferior vena cava aneurysm embolus in the renal vein discovered on physical examination 3 months ago. The left renal tumor was 14 cm, the diameter of the left renal vein was 5 cm, and the level of tumor embolism was grade 2, reaching the level above the hepatic portal vein. After 2 months of molecular targeted drug therapy, the patient was reviewed and found that the left renal tumor had shrunk to 11 cm, the diameter of the renal vein was 3.5 cm, and the level of tumor thrombus in the inferior vena cava was grade 1 and had regressed to below the level of the portal vein in the inferior vena cava. He was admitted to the hospital 2 weeks ago for evaluation, and was excluded from contraindication to surgery, and underwent radical left renal cancer surgery + left renal vein and inferior vena cava tumor thrombus removal. The operation went smoothly and the patient recovered well after the operation and was discharged from the hospital. Postoperative pathology: grade 4 clear cell carcinoma of the left kidney with some regional sarcoma-like changes and regional necrosis was seen. Conclusion: The application of preoperative molecular targeting drugs benefited some patients with tumor shrinkage and regression of cancer thrombus, which reduced the risk of surgery to some extent.