The invention discloses a method for preparing large-size high-quality graphene with controllable number of layers, wherein graphite powder or flake graphite is mainly adopted as a raw material. The method specifically comprises the steps of intercalating the graphite raw material by virtue of an intercalating agent to initially weaken the intercalation interaction force and obtain different orders of graphite intercalation compounds (GICs); soaking the GICs in an appropriate expander, and then under the case that an auxiliary agent is added or not, enabling the intercalation materials to be quickly reacted with the expander to release a gases to obtain highly expanded wormlike graphene aggregate and further to cause the distances among graphene lamellar layers to be increased; and after certain processing, peeling, and then repeatedly centrifuging and dispersing to obtain a graphene dispersion with different numbers of layers. According to the method disclosed by the invention, the intercalation-expansion-peeling process is involved, raw materials are cheap, the reaction process is simple and easily controlled, and the number of layers of graphene is precisely controlled; the obtained graphene lamellar layers have the advantages of few defects, large size, high conductivity, high yield and the like, the large-scale industrial production is easily implemented, and the problems of high cost, low productivity, poor quality, small size, uncontrollable number of layers and the like in an existing graphene preparation technology are solved.