With the accelerated development of new power systems, the power system is gradually transitioning from a load-following model to an interactive load-generation model. As a high-quality load-side regulation resource, the load from the aluminium smelting industry possesses significant regulation potential. This paper proposes a strategy for aluminium smelting load participation in secondary frequency regulation control of the power system, considering the dynamic allocation of AGC signals. First, a regulation characteristic model for electrolytic aluminium load is established, and a two-region power system frequency regulation response model incorporating electrolytic aluminium load is developed. Then, considering both frequency regulation capacity and regulation rate characteristics, a dynamic power allocation strategy for secondary frequency regulation is proposed, enabling real-time dynamic allocation of secondary frequency regulation power between thermal power units and electrolytic aluminium load based on changes in AGC signals. Next, considering factors such as AGC control effectiveness and costs, a multi-objective optimisation method for secondary frequency regulation control parameters based on the NSGA-II algorithm is proposed to further enhance frequency regulation performance; finally, the proposed control strategy is validated through Matlab/Simulink simulation. The results indicate that the proposed secondary frequency regulation control strategy fully utilises the regulation characteristics of different regulation resources, playing a positive role in improving secondary frequency regulation effectiveness, and the system's frequency characteristics are improved to a certain extent.