This invention belongs to the field of building materials technology and specifically relates to a self-compacting high-strength mortar, which is composed of cement, stone powder, silica fume, expansive agent, and water reducer in a certain proportion. The mentioned cement is one of silicate cement or ordinary Portland cement, the stone powder is double-fly ash, and the water reducer is polycarboxylate water reducer. This invention, by adopting a new type of water reducer, minimizes the loss of mortar's workability over time, with its flowability essentially remaining unchanged within 2 hours, and achieves a 28-day compressive strength of over 70 to 90 MPa, which can enhance the convenience of construction. The invention uses silicate cement or ordinary Portland cement combined with yellow sand to prepare high-strength mortar, significantly reducing production costs and making it easy to use on a large scale. The preparation method of this invention is simple and widely applicable.