Solar-driven carbon dioxide (CO₂) reforming of methane (CH₄) simultaneously converts CO₂ and CH₄ (both are greenhouse gases) into syngas (H₂ and CO), a valuable industrial chemical, as well as stores intermittent solar energy in the form of chemical energy; thus, it has received increasing attention. Compared to traditional solar thermochemical reforming, which requires a reaction temperature as high as ~ 900°C, photothermal reforming has been demonstrated to be performed at much lower temperatures and resultantly to achieve higher energy conversion efficiency. Much progress has been made in the development of efficient photothermal catalysts with high quantum efficiency. However, in these studies, experiments were performed in the kettle reactors which have low photon transport efficiency; thus, the solar-to-fuel (STF) energy conversion efficiency is as low as ~ 30%. Therefore, the motivation of this work is to design an efficient photothermal reactor based on multiphysics simulations. A multiphysics model, including the absorption and transport of photons, heat and mass transfer, and reaction kinetics, was developed. We quantitatively analyzed the sources and distributions of energy losses with and without heat recovery at the reactor-scale. Results show that heat recovery can reduce the sensible heat loss of gas by absolute 5%, but volumetric radiation loss still exceeds 15%. Therefore, to further enhance the STF efficiency, much efforts should be made on reducing the reaction temperature, for example, by taking advantage of more significant photothermal effect.