The austenite fraction dependence on temperature in grain-oriented silicon steel was determined by physical simulation. The change in the temperature distribution along strip thickness of grain-oriented silicon steel during the hot rolling process was studied by the finite element method. Based on the data obtained, the phase composition variation in the strip was determined. It is shown that the temperature gradient across the strip thickness of grain-oriented silicon steel leads to inhomogeneous distribution of austenite in the steel structure. The different contents of phase components across the strip thickness can lead to different processes of structure formation for different strip thicknesses (dynamic and static recrystallization, phase transformation). As a result, a structure that is heterogeneous across the strip thickness can form during hot rolling of grain-oriented silicon steel.