A 561-bp complete open reading frame of the duck enteritis virus(DEV) UL55 gene (GenBank accession No EU071034) was isolated in our laboratory and amplified by common PCR using a pair of specific primers .PCR product containing this ORF was cloned into the vector of PMD18-T. Four evolutionary analysis approaches were used to construct phylogenetic trees of DEV in relation to herpesviruses based on the nucleotide sequences. Bootstrap was used as statistic method to testify the reliablity of the constructed phylogenetic tree. Phylogenetic trees indicated that DEV and other herpesviruses generated from one ancestor and DEV were grouped into the subfamily Alphaherpesvirinae. In our result, DEV showed a close relationship with the genus Mardivirus, but formed a single branch. Partial genomic organization and phylogenetic analysis in the present study provides evidence that DEV was a member of the subfamily Alphaherpesvirinae and should be assigned as an individual genus or group.