Aim To examine the role of peroxisome proliferators-activated receptorα(JPPARα) in myocardial fibrosis induced by angiotensinⅡ(AngⅡ)in vitro. Methods Cardial fibroblasts(CFs) of neonatal Wistar rats were isolated and cultured,then was stimulated with AngⅡ.CFs proliferation was measured by thiazolyl blue(MTT)assay.mRNA expression of collagenⅠ,collagenⅢ,matrix metalloproteinase 2(MMP-2) was measured by reverse transcription-polymerase chain reaction,reactive oxygen species levels in CFs were detected with DCFH-DA. Results Compared with control group,after treatment with AngⅡfor 12 hours,MTT value of cardial fibroblasts was increased,mRNA expression of collagenⅠ,collagenⅢ in CFs was increased,and MMP-2 was decreased significantly;the increasing of reactive oxygen species(ROS) levels in CFs was also showed with fluorescence stain;Bezafibrate,a kind of JPPARα activators,inhibited the above changes with no effect on CFs proliferation;MK886,a kind of JPPARα antagon,abrogated the action of Bezafibrate. Conclution The results suggest that JPPARα-dependent pathway is critically involved in the inhibition of myocardial fibrosis in vitro,which may be through inhibiting the generation of ROS.