The solar-assisted methane steam reforming (SAMSR) process is an efficient hydrogen production technology. Volumetric solar receivers with an internal porous absorber can be used to concentrate the solar energy to provide proper conditions for MSR reactions. In this study, first, a sensitivity analysis is performed on effective design parameters of a conventional SAMSR reactor, including the inlet gas direction, internal porous medium properties, and use of a porous medium in the preheating conduit. Next, a new design is proposed – using outlet hot gas of reactor to preheat the feed gas – and its effects on the hydrogen production rate are analyzed to find the best configuration with the highest hydrogen production rate. Finally, the effect of feed gas flow rate on hydrogen production is studied in the optimal case and the results are compared with those of a conventional design. Results show that preheating improves the hydrogen production rate by about 20% in the direct case. Also, the optimal arrangement of the internal porous media in the direct case could improve the hydrogen production rate by 116%. The final case provides an extra 20% improvement in hydrogen production by the proper configuration of porous media in the preheating channel.