Abstract:The construction scale of power transmission and transformation projects has been rapidly developed, and the corresponding amount of power grid cost data continues to increase. However, at present, the mining and processing of project cost data cost is far from enough. It is urgent to improve the informatization level of cost management and construct the "big data" system for the cost of power transmission and transformation project. Based on the current situation of data management of power transmission and transformation engineering under the background of big data application,this paper analyzes the necessity and significance of the application of big data theory in engineering cost management, The application of the cost data collection, storage technology and key influencing factors of the transmission and transformation project is discussed. The types of the cost data sources, the data analysis and processing flow, the direction of the data mining and application are systematically summarized and summarized, and the platform of the transmission and transformation project cost system based on the big data application is constructed and combined. and the key influencing factors are found through the analysis of practical application cases. The scientific cost prediction model is established by means of support vector machine and particle swarm, which can provide a heavy burden for the improvement of cost management and control level of power transmission and Transformation Engineering in power grid enterprises.