OBJECTIVE： To investigate the effects of Buyang huanwu decoction on the expression of MMPs and TIMPs in cardiac tissue of viral myocarditis （VMC） model mice. METHODS： Male BALb/c mice were randomly divided into control group， model group， positive control group [captopril， 100 mg/（kg·d）]， Buyang huanwu decoction low-dose， medium-dose and high-dose groups [6， 18， 36 g/（kg·d）]， with 24 mice in each group. Except for control group， other groups were given Coxsackie virus B3 once intraperitoneally to induce VMC model. After modeling， control group and model group were given constant volume of normal saline intragastrically； administration groups were given relevant medicine intragastrically； once a day， for consecutive 30 days. The general situation of mice in each group was observed. The day of inoculation was set at 0 d， heart mass to body mass ratio （HW/BW） was measured at 4， 10， 20， 30 d after inoculation. The morphological characteristics of myocardium were observed by HE staining， and the myocardial histopathological scores of myocardium were evaluated. The distribution of type Ⅰ and Ⅲ collagen in myocardium was observed by Abcam picrosirius red staining， and the ratio of type Ⅰ to Ⅲ collagen was calculated. At 30 d， relative expressions of MMP-1， MMP-3， MMP-9 and TIMP-1 in cardiac tissue were detected by Western blotting assay， and the ratio of MMPs to TIMPs was calculated. RESULTS： Compared with control group， mice in model group suffered from irritability， arch back， alleviation of stimulation response， reduction of body mass and even mental depression. Typical inflammatory changes and local interstitial hyperemia were observed in the myocardium， accompanied by a large number of lymphocyte infiltration and distribution of type Ⅰ and Ⅲ collagen. HW/BW （at different time points of 10-30 d）， myocardial histopathological score （at different time points of 4-30 d）， ratio of type Ⅰ and Ⅲ collagen （at different time points of 4-30 d）， the expression of MMP-1 and MMP-9， ratio of MMPs to TIMPs were increased significantly， while the expression of MMP-3 and TIMP-1 were decreased significantly （P＜0.05）. Compared with model group， above symptoms of mice in administration groups were improved to different extents. HW/BW [at different time points of 10-30 d in administration groups （except for 10 d in Buyang huanwu decoction low-dose group）]， myocardial histopathological score （at different time points of 10-30 d in administration groups）， ratio of type Ⅰand Ⅲ collagen （at different time points of 4-10 d in positive control group and Buyang huanwu decoction high-dose group， at different time points of 20-30 d in Buyang huanwu decoction low-dose and medium-dose groups）， the expression of MMP-1 （positive control group and Buyang huanwu decoction high-dose group） and MMP-9 （administration groups）， ratio of MMPs to TIMPs （administration groups） were decreased significantly， while the expression of MMP-3 （positive control group， Buyang huanwu decoction low-dose and high-dose groups） and TIMP-1 （administration groups） were increased significantly （P＜0.05）. CONCLUSIONS： Buyang huanwu decoction can inhibit myocardial fibrosis of VMC model mice by inhibiting myocardial collagen hyperplasia， regulating the expression of MMPs and TIMPs， improving MMPs/TIMPs imbalance.