Security constrained economic dispatch is relatively mature in dispatch and control for the provincial power grid. In order to achieve large-scale optimal allocation of resources, it is necessary to study security-constrained economic dispatch technology for the interconnected power grid. In view of the difficulties encountered in actual production and operation, five key problems of optimization target design, system balance, tie-line adjustment, and basic data integration are refined, and various solution strategies are given for each problem. The scenario construction method of security-constrained economic dispatch for an interconnected power grid based on strategy combination is established, and the adaptability to different scenarios and the characteristics of corresponding models are analyzed. Finally, the rationality and accuracy of the strategy combination are verified through practical grid calculation examples. Guided by actual needs, constructing different application scenarios and economic dispatch models can improve the practicality and adaptability of security-constrained economic dispatch technology for the interconnected power grid. This work is supported by the Science and Technology Project of the Headquarters of State Grid Corporation of China (No. 52110418002A).