The invention provides a high-performance thermosetting epoxy resin adhesive for roads and bridges. The adhesive comprises a component A and a component B, wherein, the component A comprises the following components in parts by mass: 100 parts of epoxy resin, 25 to 33 parts of flexibilizer, and 5 to 10 parts of diluent; the component B comprises the following components in parts by mass: 80 to 120 parts of curing agent, 5 to 10 parts of accelerant, 0.5 to 2 parts of coupling agent, 1 to 10 parts of reinforcing agent, and 0.2 to 0.5 part of antifoaming agent; and the ratio of the component A to the component B is 100:100-100:120. According to the adhesive, a flexible long-chain aliphatic amine serving as the curing agent has a curing reaction with the epoxy resin to form a solid crosslinking structure, so that the epoxy resin adhesive is high in adhesion capability and water resistance; The toughness of the epoxy asphalt adhesive is improved by adopting the soybean oil-based polyurethane to be adapted to the flexibility of a steel plate, and the soybean oil-based polyurethane containing massive hydroxyl has good compatibility with the epoxy resin. The adhesive is applicable to adhesion and waterproofing of steel bridge decks, viaducts, cement concrete bridge decks, tunnels, expressways and other decks. The invention discloses a preparation method of the high-performance thermosetting epoxy resin adhesive.