The invention discloses a method for preparing a monodisperse metal atom/graphene composite material employing electrochemical dissolved graphite. The method comprises the steps of (1) preparing an electrode from a graphite-based material; (2) electrolyzing the prepared electrode in an electrolytic cell, carrying out solid-liquid separation and recycling an electrolyte; (3) further stripping the solid obtained by separation and carrying out solid-liquid separation to obtain a crude monodisperse metal atom/graphene composite material; (4) separating and purifying the crude monodisperse metal atom/graphene composite material; and (5) carrying out thermal treatment on the composite material obtained in the step (4) under inert atmosphere protection and cooling and drying the material to obtain a monodisperse metal atom/graphene composite catalyst. The preparation method is simple in process steps, high in efficiency and low in energy consumption, and massive production can be achieved.