Abstract: A 220 kV digital substation in Inner Mongolia Power Grid has been operating for a long time, and the reliability of equipment operation has been reduced. The intelligent technology transformation has been carried out. The key technologies, process management and solutions for the intelligent transformation of the substation have been analyzed and discussed. The intelligent framework of "three layers and two networks" (station control layer, bay layer, process layer, station control layer network, process layer network) has been established. The optimized screen formation scheme has been adopted to digitize the information of the whole station. Based on networking of communication platform and standardization of information sharing, it can automatically complete information collection, measurement, control, protection, metering and monitoring, and can support advanced functions such as real-time automatic control, intelligent regulation, online analysis and decision-making, and collaborative interaction of power grid as required, effectively improving the operation reliability of digital substation.