In the context of the “dual carbon” strategy,increasing the ratio of pellets in furnace charges is the key way to achieve low-carbon transformation in the steel industry. The structural stability of pellets inside the blast furnace is crucial for their smelting performance and operational efficiency. However,traditional evaluation methods based on cold-state compressive strength struggle to accurately reflect their true mechanical behavior in high-temperature reduction environments. Therefore,a self-developed in-situ experimental platform is used to systematically investigate the evolution law of thermal compressive strength of oxidized pellets during non-isothermal reduction process. The results indicate that the thermal strength of the pellets is significantly correlated with the reduction process. Overall,the decrease decreases with the advancement of the reduction reaction,dropping rapidly from 2 632. 4 N/ P at 500 ℃ to 320. 2 N/ P at 1 050 ℃,mainly due to structural evolution caused by phase transitions at different reduction stages. In the early stages of reduction,the decrease in strength is particularly significant. During this phase,the transformation of Fe2 O3 to Fe3 O4 is accompanied by a substantial increase in volume,which leads to the breakdown of the intergranular structure and the formation of a large number of pores. It is worth noting that at 900 ℃,the formation of low-melting-point liquid phase promotes the formation of interparticle bridging structures,thereby enhancing local structural stability and causing a temporary rebound in thermal strength. In the late reduction stage,the formation of metallic Fe and its intercrystallization further strengthen the bridging between particles,but the high-temperature softening effect limits the improvement of thermal strength. The mechanical behavior and structural evolution laws of pellets are systematically clarified under blast furnace smelting conditions,the necessity of evaluating thermal compressive strength is demonstrated,and theoretical support for stable smelting with high pellet ratios in blast furnaces is provided.