Objective:To study the expression of LyGDI in lung cancer tissue and normal lung tissue, and its role in occurrence and development of lung carcinoma and its effect to radiotherapy and chemotherapy for lung cancer, to offer theoretical base for clinical diagnosis and therapy of lung cancer.Methods: (1) The differentical protein expression of LyGDI in lung cancer tissue, its corresponding normal lung tissue and normal lung tissue was analyzed by western blot hybridization and immunohistochemistry. (2) Using RT-PCR method to detect differentical expression of LyGDI in lung cancer tissue, its corresponding normal lung tissue and normal lung tissue from mRNA gene level. (3) LyGDI and negative LyGDI plasmid vector were stably transfected into A549 cells. Deal A549 cells after transfected with different concentration of DDP, to study chemosensitivity of these two kinds of cells by MTT methods; To study the radiosensitivity of these two kinds of cells exposed to different dose of 60Coγray by colone methods and detect the change of cell cycle by flow cytometry.Result: (1) In 39 samples, the results of Western Blot suggested that the expression of LyGDI was overexpresse in lung cancer compared with the corresponding normal lung issue in 29 cases (P<0.05). The expression of LyGDI was no significant differents between SCLC(small cell lung cancer) and NSCLC(non-small cell lung cancer)( P﹥0.05). In NSCLC, the expression of LyGDI was associated with lymph node metastasis(P<0.05), but it did not seem to vary with gender, age, pathology, tissue differentiation and stage( P﹥0.05). The results of Immunohistochemistry and RT-PCR were similar with the Western Blot. (2) Deal cells after transfected with DDP and 60Coγray, the survival ratio of stably transfected A549-LyGDI cells was significantly lower than contrast group. (3) To detected cell cycle by flow cytometry, the results showed that cells after transfected exposed to 60Coγray could induce the block in G2 period, there was significantly difference compared with contrast group.Conclusions: (1) The overexpress of LyGDI in lung cancer tissue was associated with lymph node metastasis. (2) Stably transfect LyGDI to A549 cells could inhibit the cell proliferation and invasion ability of A549 cells. (3) Stably transfect LyGDI to A549 cells could enhance the radiosensitivity and chemosensitivity of A549 cells.