Objective To study the possible mechanism of Huoxue Chubi Decoction in the treatment of scleroderma.Methods Thirty mice were divided into blank group

model group and traditional Chinese medicine group with high

medium and low dose

6 rats in each group. Except the blank group

the mice were intradermal injected with bleomycin hydrochloride 400 μg for 3 weeks to establish scleroderma mouse model. From the forth week till the seventh week

the rats in blank group and the model group were gavaged with the same amount of distilled water

the rats in traditional Chinese medicine group with high

medium and low dose were unitedly gavaged with Huoxue Chubi Decoction44. 8

22. 4

11. 2 g /（ kg·d）

once a day. Pathological changes of skin and lung of mice in each group would be observed

skin thickness

collagen index and levels of tissue reactive oxygen species（ ROS） would be compared.Results In the model group

the dermis was significantly thickened

and the collagen fibers were increased obviously

and the infiltration of inflammatory cells was accompanied; In the lung tissue

the alveolar septal thickening accompanied with a large amount of monocyte infiltration

and there is fibroblast proliferation. in the gap between the thickening alveolar septal and monocytes. Compared with the model group

the degree of thickening of dermal collagen fibers and alveolar septal were reduced in traditional Chinese medicine group with different dosage. Skin thickness

collagen index and lesion ROS content in the model group were significantly increased than those in the model group（ P < 0. 01）; Compared with the model group

the skin thickness and collagen index were significantly lower in the high

medium and low dose groups of traditional Chinese medicine

the lesion ROS content of the traditional Chinese medicine group was higher and the middle dose was lower（ P < 0. 05 or P < 0. 01）. Conclusion Huoxue Chubi Decoction can significantly reduce the skin thickness and collagen index in scleroderma mouse model

the mechanism may be related to decreasing the level of ROS in the lesions.