The invention relates to a high-strength adhesive as well as a preparation method and application thereof. The high-strength adhesive comprises liquid epoxy resin, a modifier and curing agents. The high-strength adhesive has the beneficial effects that the high-strength adhesive is used for preparing buoyancy materials, the buoyancy materials bonded and coated with the high-strength adhesive have the characteristic of high hydrostatic pressure strength, and the water absorption of the buoyancy materials in the range of 30-120MPa is less than 1%, therefore, the finished products of the buoyancy materials formed after the buoyancy materials produced with the adhesive are bonded and coated with the adhesive can absolutely meet the requirements of 3000-11500m deep sea detection devices.