The steam reforming reaction is widely used for obtaining syngas, a mixture of hydrogen and carbon monoxide. The process consist of two reactions - the reforming and water-gas-shift reaction. The reforming reaction has a strong endothermic character, what means it requires huge and continuous heat supply to proceed. Due to the process character, a highly non-uniform temperature field develops inside the reactor. It has a consequence in large temperature gradients, leading to the catalyst degradation and reduced lifetime of the reforming unit. The aim of the presented research is to unify the temperature field developing in the reactor, for easier control of the process and extension of the reformer's life expectancy. A conventional plug-flow reactor consist of a cylindrical pipe body, filled with catalyst. The presented methodology included optimization of the catalyst distribution in the reactor, as to acquire the most uniform temperature field possible. A genetic algorithm was chosen to be the mean of finding the most advantageous alignment of the catalyst. It is an example of evolutionary algorithms, basing on rules similar to natural selection. The algorithm generates a random, initial population of reactors and calls the reforming simulation over each of them. The computation results are then evaluated and ranked using predefined fitness functions. The ranked reactors parameters' are further recombined with selection probability based on the fitness values, until a whole new population is created and the algorithm's loop restarts. The higher the fitness value of a specific reactor, the higher are the chances of passing its segments composition to the proceeding generation. The fitness computation leaves a vast space for improvements, as it may be computed basing on many different process' parameters. This work focuses on distinguishing differences in the algorithm performance, depending on the formula for fitness calculation. The algorithm's converging speed, overall fitness values of specimens and optimization results were investigated and compared.