To address the limited heat transfer capacity of hydrated salt thermal chemical storage materials, a multi-physics model coupling heat transfer, flow, and reaction within a shell-and-tube hydrated salt reactor is developed. Through the application of a topology optimization approach, a high-performance fin structure suitable for thermal chemical storage reactors is devised. The impact of fin volume is analyzed, leading to the identification of an optimal high thermal conductivity material volume fraction of 15%. Subsequently, the topology-optimized structure is compared with reactors equipped with traditional straight fins and those without fins installed, analyzing the effects of various parameters on the thermal storage performance of the reactor. The results indicate that during the thermal storage process, compared to reactors without fins and reactors with straight fins having the same high thermal conductivity material volume fraction, the topology-optimized fins reduce reaction times by 84.5% and 53.9%, respectively. In addition, the topology-optimized structure exhibits better thermal storage performance than the reactor with straight fins under different reaction kinetic coefficients and thermal conductivities. With increasing reaction kinetics coefficients and decreasing thermal conductivity coefficients, the enhancing effect of the topology-optimized structure significantly increases, thus demonstrating the superiority of the topology optimization design proposed in this paper and providing valuable references for strengthening the thermal chemical storage performance. © 2024 Xi'an Jiaotong University. All rights reserved.