The main aim of this research was to explore the factor structure of risk sources and the dimensions of perceived risk by consumers inB2C E Commerce, and investigated the impact of the risk factors on the perceived overall risk. 48 subjects were interviewed and 635 subjects surveyed by the questionnaire. In this study, eight factors of the risk resources were explored by exploratory factor analysis and then tested by structure equation model. The seven dimensions of the perceived risk were ascertained by confirmatory factor analysis. The more important risk factors of the perceived overall risks were confirmed by regression. The findings suggest that the core risks are mostly brought from the cyber reality interface in B2C E Commerce.