Straw fiber and steel slag are typical agricultural and industrial by-products, respectively. By preparing foamed concrete, straw fiber and steel slag can be prepared into biomass low-carbon building materials to realize resource recycling. In this study, steel slag was used as the main cementitious material, and rice straw fiber was added to prepare straw fiber reinforced alkali-activated steel slag-based foamed concrete. The effects of hydrogen peroxide content, straw content and curing conditions on compressive strength, thermal conductivity, pore structure and CO₂ sequestration of straw fiber reinforced alkali-activated steel slag-based foamed concrete were studied. The results show that the hydrogen peroxide content can effectively adjust the bulk density, compressive strength and thermal conductivity of the straw fiber reinforced alkali-activated steel slag-based foamed concrete, and the straw fibers can increase the pore connectivity and facilitate the internal diffusion of CO₂. At the same time, the mechanical properties of straw fiber reinforced foamed concrete need to balance the two effects of matrix enhancement and pore structure destruction.