Abstract: At present, the UHV grid construction and the clean energy utilization bring China new opportunities and challenges to the development of power industry. At the same time, the electric power system reform will actively promote the optimization of distribution network, as well as rapid development of the wind, solar, biomass and other renewable energy power generation, to bring new challenges to electric power design industry. As the source part of power grid project, electric power design is a significant component of full-life cycle management. Under the background of the current development of Chinese power grid, how to improve the management of electric power design and the quality of design projects in a preferable way has become an important work. Therefore, it can provide a reliable guarantee for the construction, operation and maintenance of the grid, improving the power supply reliability, and reducing safety risks and hazards among grid operation. Based on the internal development need of the design enterprise, the normal business management system only involves the basic business information and hardly satisfies the requirement of design quality control. With the popularization of big data technology, data mining technology plays an increasingly important role in engineering application. As the perfect combination of artificial intelligence and database, data mining technology is used to find out potential relationships and potential rules that exist among massive databases. Up till the present, it has already become an intelligent decision-making method and an important way for decision-knowledge acquisition, and it has enormous value for research and application in the decision support system. On the basis, this paper analyzes and designs the demand of power design decision support in details, and it proposes a quality management platform for electric power design based on data mining, building the overall framework and analyzing the key data processing techniques, according to the practice with actual work. This platform aims to extracting valuable information among power grid, designers, outsource companies and customers, realizing rational management for electric power design, and ensuring the safe and stable operation of power grid. The platform is a decision support system involving customers, working as the supplement and extension of the normal business system. It has the question guiding function and three functional modules, including business monitoring, comprehensive query and comprehensive analysis. Combined with data warehouse, on-line analytical processing technology and data mining technology, the platform makes full use of three-step process for mining, such as data preparation, data mining and explaining assessment, to make sure that the effective information in business data can be extracted precisely, and to meet the actual demand of electric power design decision support system. The research of this paper is of great reference value for decision-making of electric power design enterprises in current power grid market. For the next step, we will aim at refining the existing design decision-making demands and reasonably setting up electric the design warehouse to realize the multi-dimensional decision analysis model. At the same time, we will try to select rational mining algorithms to further complete the development of electric power design quality management platform.