The demand for sustainable energy has increased with growing concerns of environmental damage. H2 has attracted considerable attention as a clean and renewable energy carrier that can be used in fuel cells. Industrial H2 has been manufactured to produce synthetic gas in large-capacity plants using steam methane reforming (SMR). However, a compact H2 production system is needed that maintains production efficiency on a small scale for fuel cell applications. In this study, a three-dimensional computational fluid dynamics model of a compact steam reforming reactor was developed based on the experimental data measured in a pilot-scale charging station. Using the developed model, one can predict all the compositions of the reformate produced in the reactor and simultaneously analyze the temperatures of the product, flue gas, and the reaction tube. Therewith, case studies were conducted to compare the H2 production performance of the eight different structures and sizes of the proposed reformer. Based on the results, a design improvement strategy is proposed for an efficient small-scale SMR process.