Abstract: The invention relates to the oil refining and petrochemical industry and concerns, in particular, techniques for determining the knock rating of motor fuels. The proposed method of determining the knock rating of motor fuels involves thermostatic control of a reaction vessel of constant volume, feeding the fuel-air mixture into the vessel, atomization of the mixture under excess pressure and ignition of the mixture. The knock rating is calculated by the knocking intensity which is determined by the value of the signal from a knock sensor installed in the reaction vessel. The proposed apparatus for determining the knock rating of motor fuels comprises a reaction vessel with inlet and outlet valves and a thermostatic controller. A spark plug is installed in the reaction vessel and a knock sensor is arranged opposite the spark plug.