In many industries with automated production, the generation of pollutants poses a significant burden on the environment. Photocatalysis is considered as a promising technology due to its ability to harness sustainable sunlight energy, driving photocatalytic reactions that generate free radicals and effectively degrade organic dyes into harmless substances. In this study, we prepared a novel 2D/2D heterostructured composite of bismuth selenide and silver bismuth iodide (Bi₂Se₃/SBI) using a wet impregnation method. Crystal structure analysis revealed successful integration of Bi₂Se₃ and SBI, facilitating charge separation and transfer. In addition, Bi₂Se₃ not only served as co-catalyst but also provided unique topological surface states and photothermal conversion properties, thereby further enhancing the photocatalytic activity. As expected, the 1.0 wt% Bi₂Se₃/SBI composite catalyst exhibited optimal activity in the photodegradation toward brilliant green dye under UV-B irradiation, with a reaction rate constant of 0.0178 min-1 , which is higher than that of pristine Bi₂Se₃ and SBI. This is attributed to the synergistic effect of the heterostructure improving charge separation and photothermal conversion efficiency. This work provides a potential strategy for developing efficient photocatalysis for degrading organic pollutants.