The results of studies of radiation-chemical effects on the structural-group composition of a model mixture of n-hexane–n-hexene in the ratios 95/5, 90/10, 80/20, 60/40% under static conditions are presented. Laboratory studies were performed on a source of gamma radiation Co60 at a dose rate of P = 0.076 Gy/s in the range of absorbed doses D = 27–78 kGy. Density, viscosity, and iodine numbers of n-hexane–n-hexene mixtures were determined immediately after irradiation, and 1, 2, and 7 months after irradiation at different absorbed doses to observe post-irradiation effects. It can be seen from the IR spectra that in mixtures with a low content of n-hexene (5–10 %), the initial direction of radiation-chemical processes consists of dehydrogenation and the formation of olefins. In mixtures rich in n-hexene (20–40 %), both processes – olefin formation and polymerization – occur at the same time during gamma radiolysis. Irradiation of n-alkenes is accompanied by polymerization processes proceeding in a chain mechanism. After irradiation of the mixtures, the density and viscosity increase, and the iodine number decreases. The rate of polymerization during radiolysis of n-hexane–n-hexene mixtures depends on the concentration of olefin in the system and the absorbed dose. At doses above 45 kGy, polymerization becomes the dominant process in systems containing more than 20 % olefins.