Relevance. Developing and improving mathematical models of natural gas steam reforming is essential to enhance hydrogen and syngas production efficiency, optimize industrial equipment performance, and reduce energy consumption. Although the methane reforming is well studied, models that incorporate an extended hydrocarbon composition of natural gas (C₂–C₄), thermal effects, real reactor geometry, and validation using operational data still require further development. Aim. To develop and verify a mathematical model of the natural gas steam reforming that integrates key kinetic laws, reactor geometry, thermal effects, and actual process parameters. Methods. Chemical reaction engineering, numerical solutions of differential equations (Euler method and BDF), Arrhenius-based kinetic calculations, and optimization techniques including differential evolution and the Nelder–Mead algorithm to determine pre-exponential factors and activation energies. The model was implemented in Python. Validation comparing simulation results with literature data and industrial reactor performance. Results and conclusions. Two models were created: one based on literature data and a simplified plug flow reactor model incorporating methane steam reforming, CO shift, and CO₂ reforming reactions. Numerical calculations produced concentration profiles along the reactor and optimized kinetic parameters. The optimized values yielded product compositions at the reactor outlet close to industrial data, with a hydrogen deviation of less than 1%. The main deviation occurred in residual methane concentration, likely due to the exclusion of C₂+ pyrolysis reactions, which will be addressed in future work. Additionally, Thiele modulus analysis indicated that methane reforming reactions occur in a mixed kinetic-diffusion regime, while the CO shift reaction requires further refinement. The results confirm the validity of the proposed model and its suitability for engineering calculations, with future work focusing on expanding the kinetic scheme to include C₂+ pyrolysis reactions.