The Smart Grid, observed as the next generation power grid, uses two-way flows of electricity and information to construct a widely distributed automated energy delivery network. We investigate three major systems, explicitly the smart infrastructure system, the smart management system, and the smart protection system. In this article, we concentrate on the smart information subsystem is used to prop up information generation, modeling, integration, analysis, and optimization in the circumstance of the Smart Grid. We also propose possible future guidelines in each system. Specifically, for the smart infrastructure system, we investigate the smart information subsystem and the smart communication subsystem. We finally outline some prospect research directions and challenges.