Abstract <p>The peculiarities of soot formation are experimentally and numerically studied in the process of ethylene pyrolysis in a shock tube at different pressures. The ranges of pressure of 6−26 bar and carbon concentration of 2.8−3.8 mol/m³ were chosen for an investigation based on an analysis of the published data. The diagnostics of the soot formation process were carried out using the conventional laser extinction method. The pressure effect on the soot yield and the magnitude of the temperature decrease is found. An analysis of the data obtained is carried out on the basis of the numerical modeling using modern kinetic mechanisms of pyrolysis and oxidation of hydrocarbons. It is found that a&#xa0;significant temperature decrease in the mixture detected in the experiments is determined by the initial pyrolysis reactions, whose contribution can be different at different pressures.</p>