This paper presents a performance analysis for the autothermal reforming process of methane in a fixed bed reformer for hydrogen production. The process is simulated using a 1-D heterogeneous reactor model under small-scale conditions. The model accounts for mass and thermal dispersion in the axial direction, axial pressure distribution, and interfacial and intraparticle transport. The process performance under dynamic and steady state conditions is analyzed with respect to key operational parameters: temperatures of gas feed and catalyst bed, oxygen/carbon and steam/carbon ratios, gas hourly space velocity (GHSV), and feed contaminations. The influence of these parameters on gas temperature, methane conversion, hydrogen yield and purity, and reforming efficiency is investigated. An optimal operational window of a GHSV range from 1050 to 14,000 h-1, steam/carbon molar ratio of 4.5–6.0, and oxygen/carbon molar ratio of 0.45–0.55 is obtained to achieve a high conversion level of 93%, hydrogen purity of 73% on dry basis, thermal reformer efficiency of 78%, and a yield of 2.6 mole hydrogen per 1 mole of methane fed. The simulation studies are performed using gas feed temperature and pressure of 500 °C and 1.5 bar, respectively.