Abstract: Eight virus strains were isolated from the liver and spleen of the dead young muscovy ducks, mule duck and sheldrake characterized with symptoms of different degree dot/spot haemorrhage and necrosis in the liver. These isolates could caused the muscovy duck- embryo and chick-embryo to die that showed the hemorrhage and necrosis in embryo-livers. 1-2 old-day birds above infected with these isolates had the same character with clinically dead birds and the virus could be isolated from artificial infected birds. These isolates could proliferate in MDEF and result in CPE.The virus could proliferate in the cytoplasm in order of crystals. The viron was shown spherical, icosahedron, cubic symmetry, no-envelope,with double-layered capsid, about 70nm in diameter by electron microscopy. These isolates had no haemagglutination activity and were not sensitive with chloroform, ether and FUDR. The PAGE analysis of the viral genome revealed that isolates genome were related to avian reovirus (ARV), composed of ten segments of dsRNA (L1-3、M1-3 and S1-4). Moreover, the specific band could not be amplified from isolates by specific primers of MDRV. Above all, these isolates temporarily belong to new-type duck reovirus, Orthoreovirus Reoviridae