The invention relates to an epoxy resin adhesive. The epoxy resin adhesive comprises the following raw materials in percentage by mass: 25-66% of silicon micropowder, 10-45% of a toughening agent, 10-30% of bisphenol A type epoxy resin, 1.5-3.5% of a flame retardant, 0.05-0.5% of carbon black, 1.5-4% of phenolic aldehyde epoxy resin, 1.4-4% of dicyandiamide, 2.5-5.6% of a thixotropic agent and 1.5-3.6% of an accelerant. The epoxy resin adhesive has the advantages of low toxicity, volatility effect, wide blending ratio, strong bonding force, good toughness and high flame retardant level which can reach V-0. The preparation method of the epoxy resin adhesive comprises the following processing steps of weighting, roasting, dispersing, mixing, pressing, mixing, pressing, vacuumizing, sampling, inspecting and packaging. The preparation method has the advantages of simple process, convenience in operation and high yield and suitable for large-scale popularization and application.