Abstract: In the field of metallurgical equipment, the cracking of the roll ring of large-size Cr12MoV straightening rolls has long restricted its service life. To improve the thermal fatigue resistance and wear resistance of the roll core material, graphite steel was adopted as the roll core material, and the composite forming of the Cr12MoV roll ring and graphite steel core was realized by the centrifugal casting process. However, during the high-temperature centrifugal casting process, Cr elements in the roll ring matrix diffuse toward the core graphite steel along the temperature gradient, resulting in interfacial composition segregation. To reveal the influence law of Cr element diffusion on the microstructure and properties of as-cast graphite steel, graphite steel samples with different Cr contents(0%～1.2%) were designed in this study, and their microstructure evolution and mechanical behavior were systematically analyzed. The results show that when the Cr content increases from 0% to 1.2%, Cr increases the undercooling degree by improving the austenite stability and inhibits carbon diffusion at the same time, which refines the lamellar pearlite by about 30%～50%. With the further increase of Cr content, the content of spheroidal graphite in graphite steel decreases, and the graphite size of the 1.2%Cr sample is reduced by 73% compared with that of the Cr-free sample, which is attributed to Cr hindering the diffusion and aggregation of carbon atoms. Although the addition of Cr reduces the plasticity and toughness of the steel due to its interstitial solid solution and the aggregation of Cr atoms at grain boundaries, the Cr content of 1.2% and below has no obvious effect on the cracking risk of the roll ring. The study holds that Cr improves wear resistance through a dual mechanism. Firstly, refining the interlamellar spacing of pearlite to strengthen the matrix. Secondly, reducing the content of spheroidal graphite to weaken the lubrication effect and inhibit frictional oxidative wear at the same time, making the addition of Cr an effective way to improve the comprehensive properties of graphite steel.