Kidney cancer patients with only 30% function left in one kidney need to be discussed in different situations. If the opposite side kidney is good, the tumor can usually be removed surgically; if the opposite side kidney is failing or isolated, dialysis, kidney transplantation and other treatments are needed after surgery. For kidney cancer patients, if one kidney is suffering from kidney cancer and the affected kidney only has 30% function left, while the opposite kidney does not suffer from kidney cancer and has good function, then the kidney suffering from kidney cancer needs to be operated, and according to the size and stage of the tumor, radical nephrectomy or nephrectomy with preservation of renal unit can be chosen, and after the operation, the patient will be supplemented with comprehensive treatments, such as targeted therapy, immunotherapy and other treatments. For patients with isolated kidney or contralateral kidney failure, if they have kidney cancer and only 30% of renal function left, they need to undergo nephrectomy with preservation of renal units as much as possible; if the patient’s kidney cancer is large, only radical nephrectomy can be performed, and long-term dialysis or renal transplantation is needed after the operation. It is recommended to go to regular hospitals for comprehensive assessment of the condition, follow the doctor’s instructions and choose the appropriate treatment plan to improve the patient’s prognosis, so as to avoid delaying the condition.