An intelligent decision-making system for power grid planning is designed and implemented on a unified platform to cope with the situation of large amounts of data，complex decision and the lack of technical tools. With the function of visualization and advanced decision-making，the system，embedded with a comprehensive built-in database，is closely merged with the geographical information system（GIS）. The system has functions including adaptability evaluation，project prioritization，differentiated planning，and data interface to power system simulator. In the process of auxiliary decision-making，coordination assessment of power plants and power grid is conducted through power grid scheduling simulation，power grid expansion projects are prioritized following the fundamental principle of steady-state security analysis，the skeleton parts of a power grid are identified by a graph theoretical algorithm，and power system reconfiguration with initialized model data for commercial simulation software is produced from a planning scheme by applying the newly developed data interface to power system simulator. The software system is designed and developed from a practical point of view，and the design concepts and implementation methods proposed in the paper are verified by its preliminary applications in Hubei power grid.