Objective To investigate the diagnosis of renal malignant tumors. Methods 24 patients under went the intravenous urogram ,B-mode ultrasonograms and CT features of renal malignant tumors which were found in the cases of operation and pathologically confirmed were retrospectively analysed. Results All the 24 cases only five casees is display by IYP,nineteen cases is display by B-US,all cases is display by CT. Conclusion The correct diagnostic rate of renal malignant tumors can be increased through synthetical application of techniques. CT possesses important value in diagnosis, treatment and estimating the pronosis.