Enterohemorrhagic Escherichia coli (EHEC) O157:H7 is an important pathogen which endangers human health. The severity of disease,the lack of effective treatment and the potential for large-scale epidemic outbreaks from contaminated food supplies have propelled researches on the pathogenesis of O157:H7. This article reviews the recent developments in the research of Escherichia coli O157:H7 genome and major plasmid pO157 which are related to its virulence.