Micro-electro-mechanical systems and a preparation method thereof are provided. The micro-electro-mechanical systems include first fixed comb fingers, second fixed comb fingers, a support beam, a movable platform, and movable comb fingers. The first fixed comb fingers and the second fixed comb fingers are fastened to a substrate, and the first fixed comb fingers are electrically isolated from the second fixed comb fingers. Two ends of the support beam are fastened to the substrate, and the movable platform is coupled to the support beam. The movable comb fingers are coupled to the movable platform, and form a three-layer comb finger structure with the first fixed comb fingers and the second fixed comb fingers. This structure improves drive efficiency of the micro-electro-mechanical systems.