The killing experiment via photodynamic therapy (PDT) was carried on 30 Kunming mice inoculated with Louis lung cancer. The tumor suppressing rates and curves were observed between the experimental group and control group. Significant differences in the tumor growth curve (P<0.05), tumor mass and tumor volume existed between the two groups (P<0.01). The tumor suppressing rates of tumor volume and mass were 52.94% and 37.24%, respectively, in the experimental group. The results revealed selective injurious effect and growth suppressing effect of photodynamic therapy (PDT) on tumor cells, it is suggested that PDT can regulate the immune function for the mice inoculated with Louis lung cancer. Photodynamic therapy (PDT) will be a available therapy for malignant tumors.