The invention discloses a graphene-glass fiber composite material and a preparation method thereof. Crosslinking of glass fibers can be realized by means of the swelling and fusing actions of grapheneoxide coatings on the surfaces of the glass fibers. Graphene oxide is taken as a sizing agent as well as a crosslinking agent with which the glass fibers can be coated uniformly, the crosslinking process is rapid and easy, and high crosslinking strength is achieved. Through further reduction, a graphene oxide crosslinking layer is turned into a graphene crosslinking layer, so that mutual action among the glass fibers is enhanced, contact resistance among the fibers is lowered, and the glass fibers show excellent mechanical performance, electric conductivity and heat conductivity and can be applied to a wild phase of the composite material. The method for crosslinking the glass fibers with the graphene has a great researching value and a wide application prospect.