The e-business strategies ultimately pursue creating the maximal value for customers through the competitive advantages and business opportunities newly created on the basis of information technologies. For the realization of e-business strategies, the successful implementation and operation of e-business system must be the crucial activities in and out of an organization. Therefore, in physical world, there were lots of interests that what kind of key factors can lead the success of e-business system. Moreover, in the field of academia also, there have been many research results for investigating and finding out the key success factors for e-business system. However, the perceptual level of the significance of key success factors that organization members perceive can be changed over each phase of system life cycle such phases as introduction, growth, maturity, and decline. This study investigated that there might be significant differences in the perceptual level regarding importance of success factors among phases of system life cycle.