OBJECTIVE：To study the improvement effects of Weijing deco ction on AECOPD model rats and its possibile mechanism. METHODS ：Totally 55 male SD rats were randomly divided into normal group ，model group ，Weijing decoction low-dose and high-dose groups （8.37，16.74 g/kg，by crude drug ），dexamethasone group （positive control group ，0.09 mg/kg），with 11 rats in each group. Except for normal group ，AECOPD model was induced by cigarettes combined with lipopolysaccharide in other groups. After modeling ，normal group and model group were given constant volume of water intragastrically ，and other groups were given relevant medicine intragastrocally ，twice a day ，for 14 days. After last intragastric administration ，the serum level of IL- 1 β was determined，and pathological changes of lung tissue and bronchus were observed in each group ；mRNA expression of MMP-9 and TIMP- 1 genes in lung tissue were detected ；protein expression of Ras homologous gene family member （RhoA）， dishevelled associated activator of morphogenesis- 1（DAAM1）and hyperplasic suppress gene （HSG）in lung tissue were also determined. RESULTS ：Compared with normal group ，the levels of IL- 1β in serum，mRNA expression of MMP- 9 and TIMP-1 as well as protein expression of RhoA and DAAM 1 in lung tissue were increased significantly in the model group（P＜0.05），while protein expression of HSG in lung tissue was decreased significantly （P＜0.05）；there were many chronic inflammatory cells infiltrating around the bronchus ，some airway mucosa epithelium exfoliating ，alveolar compensatory dilation，pulmonary septal capillary dilation and hyperemia. Compared with model group ，the levels of IL- 1β in serum，mRNA expression of MMP- 9 and TIMP- 1 in lung tissue were decreased significantly in Weijing decoction high-dose group （P＜0.05）；the protein expression of RhoA and DAAM 1 in lung tissue were decreased significantly in Weijing decoction low-dose and high-dose groups（P＜0.05），while the protein expression of HSG in lung tissue was increased （P＜0.05）；the pathological changes of Weijing decoction high-dose group ，such as inflammatory cells infiltrating around the bronchus and shedding of airway mucosa ， were improved significantly ， and there was complete alveolar epithelium structure but no obvious pulmonary dilation. CONCLUSIONS：Weijing decoction can improve AECOPD model rats to certain extent ；its mechanism may be associated with down-regulating mRNA expression of MMP- 9 and TIMP -1 as well as protein expression of RhoA and DAAM 1 in lung tissue ， up-regulating protein expression of HSG in lung tissue so as to inhibit the airway remodeling.