The effect of low-power He-Ne laser irradiation on the function and expression of CD59 on T cells in tumor-bearing mice is studied. 40 BALB/C mice were randomly and evenly divided into four groups:tumor-bearing mice were constructed in groupⅡⅢⅣ,while groupⅠwere treated as normal control. Thymus region of mice in group Ⅲ were irradiated every day and mice in group Ⅳ were irradiated every two days. The growth of tumors were noted by tumor growth curves. The mice were executed 20 days later and T cells were segregated from thymus. The expression of CD59 on T cells from thymus was detected by immunohistochemistry and immunofluorescence;lymphocyte proliferation in thymus was detected by lymphocyte transformation test (MTT assay);IL-2 was detected by enzyme-linked immunosorbent array (ELISA);Laser scanning confocal microscope imaging of the calcium fluorescent indicator dye Fluo-3/AM was used to determine the kinetic changes of [Ca2+] in T cell endochylema. CD25+ T cells were determined by flow cytometer .The experiments show that tumor growth was inhibited after laser irradiation.The expression of CD59 protein,the proliferation of lymphocytes,level of IL-2,degree of the [Ca2+] and the expression of CD25 in group Ⅱ,Ⅲ,Ⅳ were decreased compared with group Ⅰ,but were increased in group Ⅲ,Ⅳcompared with group Ⅱ. The results indicate that the low expression of CD59 was improved after irradiation by low-power He-Ne laser,and irradiation can enhance the function of T cells.