A thermodynamic analysis is performed of the patterns of steam conversion of natural gas at temperatures of 300–600°C, pressures of 0.1–4 MPa and H2O : C molar ratios of 0.8‒1.2. Under these conditions, the reaction product is methane–hydrogen mixtures with hydrogen concentrations of 10–30 vol %. A rise in temperature, molar ratio Н2О : С, and a decrease in pressure contribute to an increase in the concentration of hydrogen in the reaction products. The thermodynamic boundaries of the process with no carbonization of the catalyst are determined. Experiments are performed to obtain methane–hydrogen mixtures from methane with an output concentration of 15–35 vol % hydrogen on industrial Ni-CrOx-Al2O3 catalyst at 325–425°C, a H2O : C molar ratio of 0.8–1.0, and atmospheric pressure. It is shown that under these conditions, the process proceeds without the formation of carbon on the catalyst.