Ni alloy substrates are highly preferred for the potential mass production of high-quality graphene through CVD method,yet our knowledge of the mechanism at the atomic level is still very limited.Here,using first-principles calculations,we find that there is synergistic effect during the segregation of C atoms in the Ni(111)substrate.Specifically,the existence of a neighboring C atom will lower the diffusion barrier of a C atom during its segregation to the surface from sublayer of the Ni(111) substrate.Using nudged elastic band (NEB) method,we performed systematic examinations on possible low energy paths of the segregation processes.Based on this.taking NiCo and NiCu alloys as prototypical examples,we further investigated the alloy effect on modulating such a synergistic effect.Interestingly,we find that the alloy effect is strongly influenced by the local structures of the dopants.Such alloy effect can be well addressed by the delicately modulated activities of the surface and sub-surface atoms in the framework of the d-band theory.