In order to construct united planning system of SGCC, the overall framework of united power grid planning and design application is proposed in this paper, of which the main principles are determined with unity, standardization and openness. The corresponding function localization and operation mode are analyzed. The power grid planning & design application can provide data, function and professional work supports, for which the data management and interactive mode are primarily designed, achieving integration of technological process and management process and connection with other applications of five united system.