We have studied the processes of structure formation during hot rolling of grain-oriented silicon steel. We have confirmed that the structure of surface layers of a hot-rolled strip forms as a result of two processes: the γ →α phase transformation and dynamic recrystallization. The central layers form as a result of recovery of deformed grains. Based on the obtained results, we have established that a structure that is inhomogeneous in the thickness of the hot-rolled strip forms due to non-uniform phase transformation. The surface layers of the strip are cooled faster than the central ones during rolling because the γ→α phase transformation proceeds more intensively in these layers. Polygonal ferrite is formed during hot rolling of the studied steels as a result of two processes: the γ→α phase transformation and dynamic recrystallization. Since the phase transformation in the central part of the strip is weak, a deformed structure is formed there.