Kidney tumors are not judged to be malignant according to their size; kidney tumors need to be clarified by pathological examination. Kidney tumors may be malignant no matter how big they are, but they may also be benign tumors, therefore, the size of kidney tumors can not be used to directly determine their nature. Urine routine, ultrasound, enhanced CT, MRI and other tests are usually needed for preliminary diagnosis, and finally, we need to rely on pathologic examination to confirm the diagnosis, i.e., renal puncture biopsy or surgical resection. Renal malignant tumors usually grow at a fast rate, and the boundary is vague, the envelope is incomplete, and the blood flow signal is very rich, which makes it easy to metastasize and spread. Early detection, diagnosis and treatment of renal malignant tumors can improve the prognosis. When kidney tumor appears, you should go to the hospital in time to clarify whether it is benign or malignant tumor, and actively cooperate with doctors for treatment.