Objective:　The activity and the clinical mechanism of CuZn-SOD in 86 cases of larger bowel carcinoma patient’s red cells are studied by the author. It is indicated that activity CuZn-SOD in the patients’ red cells is distinctly lower than that of the healthy control and that of the normal Chinese. The disparity showed in the contrast has great significance. The activity of CuZn-SOD in red cells varies with the course. The longer the different pathological and clinical classifications of larger bowel carcinoma patients varies correspondingly. With the pathological changes become severe and the pathological diversifying degree low, the activity slows down respectively. These changes are well displayed by a regular wave- like curve. Nevertheless, no obvious difference is observed in the activity of CuZn-SOD in different patients of different suffering positions.