This paper reports the fabrication of a silicon micromirror with graphene-nickel (Ni) nanocomposite beams, and evaluate the mechanical stability of the mirror in terms of resonant frequency. A novel pulse-reversed electroplating method is developed for synthesizing the nanocomposite with uniformly dispersed and high loading content of graphene. The indentation hardness and Young's modulus of the composite are enhanced by 3.5-fold and 1.4-fold, respectively, in the presence of graphene filler. During a long-term stability test, the composite micromirror shows scanning angle of ∼17° with less resonant frequency variation of 0.68% than that of 1.47% in pure Ni counterpart. It demonstrates, for the first time, the potential of graphene-Ni nanocomposite in micromechanical system applications.