Thermolysis of asphaltenes from three heavy oils was carried out at a temperature of 120 °C in a current of N 2 with the withdrawal of the resulting products from the reaction zone. Composition and structure analysis of thermolysis products showed, that at 120 °C petroleum afaltenes are subject to thermal destruction due to breaking of covalent bonds with the formation of gas, oils and resins, exceed 13 % by weight. It is established that the main directions of asphaltene thermal transformations during thermolysis are an increase aromaticity and decrease content of naphthenic and aliphatic carbon. The reactivity and thermal transformations intensity of asphaltene molecules depend on the number of reaction centers in them. Reaction centers represent a weak aliphatic heteroatomic