The stability of noble metal(111) surfaces doped with substitutional impurities were studied by molecular dynamics simulation. The atomic interaction potentials with the embedded atom method were applied in the simulation. The change of surface energy and the formation energy of surface vacancy induced by substitutional impurity were calculated. We found that the main factors effecting the surface energy of noble metal(111) surfaces are the cohesive energy and atomic radius of the substitutional impurity. The heat of solution of the binary alloy also has an important role in the influence of substitutional impurity on the formation energy of surface vacancy, along with the cohesive energy and atomic radius of substitutional impurity. Furthermore, the change of surface energy induced by substitutional impurity was used to predict the segregation of the binary alloy in the surface theoretically, yielding good agreement with the experimental results obtained by others.