Alterations in cytosolic calcium ion concentration （〔Ca²⁺〕_i）, calcium influx, calcium pump activity, morphology and function of rat type Ⅱ pneumocytes in vitro after ⁶⁰Co γ-ray radiation were observed. The results showed that 〔Ca²⁺〕_i increased markedly after 2.5 Gy irradiation and continued to increase as radiation dose increased. In the meantime, the cellular transmembrane calcium influx increased and the membrane calcium pump activity decreased significantly following irradiation, both showing marked dose-effect ralationships. Electron microscopy revealed that the cellular lamellar bodies were depleted obviously after 10 Gy radiation, suggesting that cytosolic calcium ions were transported abnormally in type Ⅱ pneumocytes after radiation, which resulted in 〔Ca²⁺〕_i increase and the normal cellular function was disturbed. This fact is possibly one of the important links in the devolopment of radiation-induced lung injury.