To investigate the changes in plasma and cytoplasmic gelsolin during radiation-induced acute lung injury, C57BL/6 mice were randomly divided into two groups for irradiation: the total body irradiation with 4 Gy and the thoracic irradiation with 20 Gy. The plasma gelsolin (pGSN) levels were detected by ELISA Kit and the cytoplasmic gelsolin (cGSN) of the lung tissue were detected by western Blot. The total cell number and the protein concentration of bronchoalveolar lavage fluid (BALF) in the right lung of thoracic irradiated mice with 20 Gy were detected. The results show that the pGSN levels in total body irradiated mice with 4 Gy decrease significantly at 24 h post-radiation. In contrast, the pGSN levels in thoracic irradiated mice with 20 Gy decline more slowly but decrease significantly at 48 h post-radiation. After that, the pGSN levels in both groups begin to recover slowly. The cGSN levels in lung tissue of both groups decrease at 24 h post-radiation, but increase significantly at 48 h post-radiation, then gradually recover. But the changes in cGSN levels of thoracic irradiated mice are more significant. The total cell number and the protein concentration of BALF in the right lung of mice treated by the thoracic irradiation with 20 Gy increase significantly at 24 h post-radiation, approximately 16 times of the control’s, then decrease and gradually become stabilized. There is a negative correlation with the cGSN levels in lung tissue of thoracic irradiated mice with 20 Gy. pGSN and cGSN may play an important role in the process of repairing acute lung injury.Cited