Abstract: OBJECTIVE To observe the clinical therapeutic effects of Shashen Maidong Decoction in treating radiation pneumonitis. METHODS 64 cases with thoracic radiotherapy who were to receive the intensity modulated radiation therapy were divided into treatment group and control group. In addition to the intensity modulated radiation therapy， patients in the treatment group were further given Shashen Maidong Decoction. Then the therapeutic effects of both groups were observed. RESULTS The occurrence rate of the treatment group was evidently lower than that of the control group(P<0.05); The treatment group experienced a higher and more stable quality of life than the control group， with better effective rate(P<0.05); The occurrence rate of Ⅲ to Ⅳ degree of bone marrow suppression in the treatment group was lower than that of the control group(P<0.05). CONCLUSION Shashen Maidong Decoction has good effects on radiation pneumonitis.