Objective] To prove the modified Maxingshigan Decoction(modified MXSGD) intervening radiation induced lung injury(RILI) through the TGF-β/Smad signaling pathway by selectively silencing the TGF-β1 gene. [Methods] (1)Total of 18 clean SD rats were randomly divided into two groups:Chinese medicine group treated with modified MXSGD and normal control group treated with saline. The serum was made after 3 days of taking drugs to prepare medicated serum. (2) The alveolar typeⅡcells were cultured. The total dose of radiation to cell was 8Gy, frequency 3.64Gy/min. The medicated serum was given to each group respectively. (3) After silencing TGF-β1 gene with RNA interference technology, the level of TGF-β1, PAI-1, CTGFmRNA was analyzed by PCR and the protein expression of Smads was measured by Western-blot. [Results] (1) Compared with rat serum group, the expressions of TGF-β1 mRNA, P-Smad2 in 10%medicated serum group were down-regulation or deceased(P<0.05).(2) Compared with rat serum group, the transcription levels of TGF-β1, and PAI-1 and CTGF were obviously suppressed after silencing TGF-β gene(P<0.05). (3) There was no significance effect on the expression of P-Smad2, P-Smad3, PAI-1mRNA and CTGF mRNA in both 10%medicated serum+siRNA group and rat serum+siRNA group(P>0.05). (4) Compared with rat serum+siRNA, the expression of Smad6 and Smad7 was increased in 10%medicated serum+siRNA group. The differences between the two groups were significant(P<0.05, P<0.01). [Conclusion] Modified MXSGD may intervene the RILI by regulating TGF-β/Smad signaling pathway.