Aim To investigate the effect of N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP) on platelet-derived growth factor (PDGF)-induced cardiac fibroblast proliferation and collagen synthesis,and the expression of JNK. Methods Neonatal rat cardiac fibroblasts were used in the experiment,the proliferation of cardiac fibroblasts was observed by MTT assay,the expression of typeⅠand type Ⅲ collagen protein in cardiac fibroblasts was detected by immunocytochemistry assay. The expression of JNK protein,phosphorylation of JNK protein and typeⅠand type Ⅲ collagen protein in cardiac fibroblasts was measured by Western Blotting analysis. Results 10 μg/L PDGF increased cell metabolic activity,expression of type Ⅰ and type Ⅲ collagen and phosphorylation of JNK,while the protein levels of JNK were not changed. 10-9 mol/L AcSDKP could inhibit cardiac fibroblasts proliferation,expression of type Ⅰ and type Ⅲ collagen and phosphorylation of JNK mediated by PDGF,while the protein levels of JNK were not significantly changed. Conclusion AcSDKP could inhibit the proliferation and collagen synthesis of cardiac fibroblasts induced by PDGF through blocking activation of JNK pathway.