The frequent exchange of power between large-scale interconnected power grids in China, the transient power angle problem of single-unit delivery and typical delivery systems is common, and the rapid and accurate estimation of grid transmission capacity is of great significance for increasing system safety and stability margin and overall operational efficiency. Based on the equal area rule, this paper analyzes the interaction between the inertia time constant and the static stability limit on the transient power transmission limit of the power grid. After the moment of inertia increases, the transient stable transmission limit is larger within a certain range; the static stability limit before and after the accident The ratio decreases and the transient stable delivery limit decreases. By introducing the K-factor, the transient stability limit of the transmission channel is quickly estimated, and the effectiveness and practicability of the proposed method are verified by a large number of analysis and calculation of the outgoing power of the transmitting system.