A genome project has been launched and aims to sequence total genome of Cotesia plutellae bracovirus (CpBV). This on-going research has identified several open reading frames (ORFs) including an EP1-like protein (ELP1). This study was intended to analyze gene expression of CpBV-ELP1 in the parasitized diamondback moth, Plutella xylostella. CpBV-ELP genomic DNA contains one intron (778 bp long). Its ORF consists of 726 bp encoding 241 amino acid residues. The hypothetical CpBV-ELP1 protein is predicted as 27,787.83 Da and possesses N-terminal signal peptide plus three potential N-glycosylation sites. Its amino acid sequence exhibits high homology with EP1 genes from C. congregata or C. karyai bracovirus. A reverse transcriptase-polymerase chain reaction (RT-PCR) indicated that CpBV-ELP1 was expressed only in P. xylostella parasitized by C. plutellae. The expression levels were measured by real time quantitative RT-PCRs during entire parasitization period at $25^{circ}C$ culturing temperature. The expression began at the first day of parasitization and increased with the parasitization period. The ORF PCR product was cloned, over-expressed, and molecular weight of the purified protein was about 30 kDa.