The invention relates to the production of olefin oligomers by a method of oligomerization of olefins, and, in particular, to a method of isolating olefin oligomerization products and decomposing the oligomerization catalyst residues. The method of isolating products of an oligomerization reaction of olefins including a terminal double bond, in which the reaction is carried out by the action of a catalyst having chromium compounds, a nitrogen-containing ligand and organoaluminum compounds, includes a step of isolating independent olefin products and a step of treating catalyst residues. Further, the method includes the following sequential steps: a) isolating at least one liquid product of the oligomerization reaction of olefins from an output stream of an oligomerization reactor; b) treating a residue with an aqueous solution of an acid; and c) separating an organic layer and an aqueous layer.