The relationship between reduction amout and forging penetration rate in the rolling process of bimetallic ring was deeply studied, and by establishing a three-dimensional finite element model of bimetallic ring, using the finite element analysis software ABAQUS, the minimum reduction amount of core roller was calculated based on the forging penetration theory of ring. Then, the numerical simulation was conducted under different reduction amounts of core roller, and the distribution laws of plastic zone in the rolling process of bimetal ring and the influence of the reduction amount of core roller on the forging penetration rate of bimetal ring were analyzed to verify that the forging penetration theory of ring could be used for the forging penetration analysis of the rolling process for bimetallic ring. The results show that when the reduction ratio is 1.0%, the bimetallic ring is completely forged, but the forging penetration rate calculated by the empirical triangle rule is 21%, indicating that the empirical triangle rule cannot effectively judge the forging penetration of the rolling process for bimetallic ring.