Abstract: With the establishment of the double carbon target and the clarification of the action plan and route to achieve the carbon peak in the power industry, the electricity spot trading mechanism has been continuously improved. Consequently, the analysis and prediction of the changes in electricity spot price data has become an urgent issue to be addressed in the process of electricity market trading. Based on the compilation methods and applications of various market composite indices both domestically and internationally, a spot composite index is proposed to measure the changes in spot prices. The results are then interpreted and analyzed to provide reference for spot market trading. Additionally, considering the current situation of inter-provincial electricity spot trading system, a spatial value transmission index is established based on the inter-provincial electricity price composite index. This enables discussions on the upstream and downstream transmission of the electricity industry chain and the coordination of resources and capital based on the current situation of the inter-provincial electricity spot trading system. The comprehensive electricity index serves as the indicator of the spot market development, inter-provincial electricity supply and demand transmission, and it also provides an early warning function. Moreover, it establishes a connection between the upstream and downstream industry chains with electricity prices, forming the interaction between energy resources and capital flows.