Abstract: Ionizing radiation can change the activity and/or the expression of mRNA, protein of Cytochrome P-450 CYP1B1, 1A1, 4A11, 2E1), consequently influence the biotransformation and biological effects of the drugs and toxi-coid metabolization. Cytochrome P-450 participated in the reduction of bioreductive drugs (including TMQ-AQ4N). Animal experiments and clinical trials show Cytochrome P-450 can be taken advantage to exert well sensitization for radiotherapy and chemotherapy.