Hydrogenation of the light mazute at various pressures and its consecutive stepwise hydrogenation at a constant pressure were carried out to investigate the effect of hydrogenation duration and hydrogen pressure on the yield and composition of hydrogenation products. The regularities in the composition of functional groups and compound groups were investigated. It was established that the elevation of the hydrogen initial pressure has only a small effect on the yield and distribution of hydrogenation products, but a significant effect on the composition of refined oil, while the time factor significantly influences both the distribution and composition of hydrogenation products but not the yield of refined oil.