Abstract: Objective: To evaluate the practicability and rationality about the model of radiation pulmonary injury of rat caused by multiple low dose exposure.Methods: 120 rats are divided randomly into control group,once high dose exposure group and multiple low dose exposure group（40 rats each group）,and radiated using different method.8 rats in every group are chosen randomly and killed on 3rd、 5th、 8th、 12th and 26th week after radiation.To observe the histological change of lungs stained with HE.And compare the different expression of IL-6 and bFGF between every groups after immunohistochemical stain.（Results: Typical） expression of radiating pneumonia and lung fibrosis are observed in once high dose exposure group and multiple low dose exposure group.In addition,the change of cell factor between two groups is concordant.Conclusion: The model of radiation pulmonary injury of rat caused by multiple low dose exposure has lots of merit,such as lower death rate,more stabilization and well practicability.