The large-scale integration of renewable energy sources with high penetration levels and strong randomness often leads to overloading of AC transmission lines. Meanwhile, in power system upgrading and construction, the controllability of the embedded voltage source converter-based high voltage direct current (VSC-HVDC) systems has not been fully exploited. To address this issue, this paper proposes a power sensitivity analysis-based embedded VSC-HVDC emergency control (SEC) to mitigate transmission overloading. First, an AC-DC power sensitivity matrix incorporating embedded VSC-HVDC is established based on the system model. Then, during real-time operation, the active power of the VSC-HVDC is adjusted to address specific AC grid overloading according to the derived sensitivity matrix. During the adjustment process, an optimization-based control method is used to minimize the total variation in DC adjustment while keeping the active power of AC transmission lines within acceptable limits. Finally, simulation verification is carried out using a modified IEEE benchmark 39-bus system, demonstrating that the proposed SEC can address AC grid overloading under various grid fault scenarios and ensure the safe operation of the entire network.