The invention discloses a method for electrochemically preparing graphene, which preferably comprises the steps of pressing a high-purity graphite raw material to form a graphite electrode, carrying out anodization through the graphite electrode by using sulfuric acid aqueous solution or acetic acid and the like mixed acid solution as an electrolyte to prepare a graphite intercalation product, and obtaining expanded graphite by high temperature or microwave and other methods; and then pressing the expanded graphite to prepare a reaction electrode, and carrying out secondary electrochemical intercalation and expansion to finally obtain laminar graphene. According to the invention, in the preparing process, potassium permanganate and other strong oxidizers are not used, and the damage of the strong oxidizers to the structure and performance of graphene are avoided; alkali metal, fuming sulfuric acid oxydol and other inflammable and explosive dangerous substances are not used, and toxic or harmful substances are not introduced, so that the production is safe and environment friendly; and at the same time, the method is simple in process flow, easy to operate, low in cost, high in yield, mild in reaction conditions and low in energy consumption, and is suitable for industrialized large-scale production.