In the presented work, the process of ethylene conversion over the HZSM-5 catalyst has been extensively investigated. It was determined that the mentioned catalyst has a sufficiently high activity in the ethylene conversion process. Analysis of the obtained products shows that the mechanism of this process is very complex. To clarify these issues, alongside studying the conversion of ethylene into gaseous and liquid substances at various temperatures over the HZSM-5 catalyst, special attention was paid to the kinetics of accumulation, the quantity of condensation products (CP) formed on the surface, and catalyst regeneration. It was determined that the catalyst's activity in this process is observed only after the formation of 6-8% CP on the surface within ~20 minutes from the start of the reaction.