[Objective] A lytic phage of Shewanella was isolated from the sewage and characterized. [Methods] Four strains of Shewanella bacteria were used as the hosts for the isolation of lytic phages from the sewage. A lytic phage against Shewanella oneidensis MR-1, which we named M1, was isolated by the double-layer agar culture method. The plaque morphology was examined. Phage particles of M1 were concentrated by ultracentrifugation and purified by CsCl gradient centrifugation. The morphology of M1 particles was examined by transmission electron microscopy. The genome of M1 was extracted and the nucleic acid was analyzed by enzyme digestion. One-step growth curve was measured. [Results] The plaques of M1 phage were round and transparent with a diameter of about 2.3 mm?2.5 mm. Transmission electron micrographs showed that M1 had an icosahedral head about 55 nm in diameter and a long contractile tail about 170 nm in length. Phage M1 belongs to the Myoviridae family. Its genome is made of linear double-stranded DNA. The infection cycle of M1 was about 15?20 min as indicated by the one-step growth curve. [Conclusion] Bacteriophage M1 belongs to the Myoviridae family. Our results provided materials for the investigation on the roles of bacteriophages in diagenetic process on the earth.