The expression levels of BAG-1, BAG-2, BAG-5 in cancer tissues were significantly downregulated compared with matched pericancerous lung tissues and were protective factors of lung adenocarcinoma (P < 0.05, OR < 1); while the expression level of BAG-4 in cancer tissues were remankably upregulated compared with the matched pericancerous lung tissues and was risk factor of lung adenocarcinoma (P < 0.05, OR > 1). The gene discussed is BAG2; the disease is lung adenocarcinoma.