Abstract: The combination of chemotherapy and radiotherapy has been playing an important part in the treatment of malignant tumors. The principal objectives of the combination are to increase local control, decrease distant metastasis and improve survival rate without increasing normal tissue injury. But the main stumbling block for any new therapeutic agent always has its toxic effects on the critical normal tissues.Considering Urea's tumoricidal effect and its nontoxic and side effect, we designed this experiment (ie. The Effects of Urea Treatment in Combination with Radiotherapy in Walker Carcinosarcoma 256). The effects and mechanisms of the combination of Urea and radiotherapy were evaluated in terms of the levels of gross pathology、histology and ultrastructure.The animal models were rats with Walker Carcinosarcoma 256 (W256) divided into four groups at random. Group one: the combination of Urea and Radiotherapy. Group two: Urea only. Group three: Radiotherapy only. Group four: Control.The results indicated that the tumors of group one grew more slowly than that of other groups and the average tumor weight of group one was Less than that of group two and group three. Among group two and group three the tumors exhibited slower growth rate than that of control group.We have also studied the morphological changes at different levels and the results have demonstrated that the combination of Urea and Radiotherapy can effectively inhibites W256 and is better than Urea treatment and radiotherapy alone.