The sigmaC-encoding gene of two muscovy duck reovirus (DRV) S14 and C4 strains were cloned and completely sequenced. The open reading frame (ORF) comprised 810 bp and encoded 269 amino acids with a predicated molecular mass of 29.5 kDa. Expressed sigmaC fusion protein in Escherichia coli BL21 strain could be detected by Western blotting under duck anti-reovirus polyclonal serum. There are two large gap insertions at the N-terminal part of the DRV sigmaC when necessary to optimize the alignment of the amino acid sequences of the DRV sigmaC had a heptapeptide repeat and leucine zipper patterns structurally related to ARV sigmaC. All DRVs grouped into one specified genogroup within Orthoreoviruses genus subgroup II. The degree of differences between the S14/C4 and ARV was only 23-24%, and 21-22%, respectively, at both the nucleotide and deduced amino acid levels, suggested that DRVs are quite different from ARVs and should give a precise classification for DRVs in Orthoreovirus genus.