The invention relates to a preparation method of a high-toughness epoxy potting material, belonging to the technical field of potting materials. According to the preparation method, nano calcium carbonate is embedded in the surfaces of prepared basalt fibers, and calcium oxide is formed by high-temperature calcinations and decomposition; the calcium oxide reacts with water and is then removed, sothat the calcium oxide particles react completely and grooves are formed in the surface of basalt; then, an expanded perlite material is mixed with the basalt fibers, the mixture is subjected to ball-milling, and the grooves formed in the basalt are effectively filled; the interiors of the basalt fiber grooves are effectively loaded with the obtained mixture subjected to high temperature expansion, so that the surfaces of basalt fibers are enabled to be rugged, and anchoring fibers are effectively formed in epoxy resin while the specific surface area is enlarged; a cross-linked structure is effectively formed inside the epoxy, and the mechanical properties and toughness strength of the epoxy potting material are improved.