Abstract: 【Abstract】 Objective To investigate the expression of brain-derived neurotrophic factor （BDNF） in lung injury induced by brain ischemia in rats. Methods 46 adult SD rats were assigned randomly to sham operation group and brain ischemia lung injury group (BILI,n=23 in each group). Rats were subjected brain ischemia and allowed to survived 3 d. After performed neurological functional severe deficit evaluation, lung edema was observed (n=5). The BDNF expression for its mRNA and protein in lung tissues was determined by using ELISA (n=5) and RT-PCR technique (n=8). The localization of BDNF was also determined by immunohistochemistry (n=5). Results After brain ischemia for 3 days, the severe neurological functional deficit and edema in lung were seen. BDNF was located in cytoplasma of smooth muscle and epithial cells in the lung. The level of BDNF mRNA (indicated by RT-PCR) and the protein level (indicated by ELISA) were all upregulated at 3 days after brain ischemia (P<0.05). Conclusion Lung edema occurred after brain ischemia in rats is concomitant with BDNF expression, which consists of the mechanism involved lung injury induced by brain ischemia.