Toll-like receptors (TLRs) are a class of pattern recognition receptors (PRRs) that recognize pathogen associated molecular patterns (PAMPs) and play an important role in the antiviral response. To determine the effect of common carp TLR9 (CcTLR9) overexpression on the expression of down-stream interferon associated immune factors in epithelioma papulosum cyprini (EPC) cells, may provide useful information for the further investigation on the anti-virus effect mediated by TLR9 in fish. In this study, we constructed an overexpression vector, pEGFP-N1-CcTLR9, by cloning the CcTLR9 gene and inserting it into an expression vector pEGFP-N1.