The single-pass thermal compression experiment of steel Q345E was carried out by Gleeble-3500D thermal simulator, and the flow stress model of steel for ring was established. Then, a 3D numerical simulation model of two-piece rolling of large-scale forging billet was established in finite element simulation software SIMUFACT, and the numerical simulation of the ring rolling process in a large inner ring was carried out in a production cycle. Furthermore, its reliability was experimentally verified, and the regulation of equivalent strain field, temperature field, rolling force and metal flow in different parts of ring were studied. The results show that the strain distribution of the ring during the rolling process is that the strains of the driving roller and the core roller between the step height, and the edge area of the ring are obviously greater than that of other areas. Otherwise, the strain becomes large when it is close to these parts, which displays that in the whole ring rolling process the deformation zone expands gradually from the contact surface and edges to inner ring. But the high temperature region of the ring becomes narrower and narrower, and is concentrated to the inside of the ring, and the temperature inside the ring is much higher than that in the contact position of driving roller and the core roller. Thus, the changing regulation of rolling force and rolling moment first increases and then fluctuates within a certain range, and finally decreases gradually.