The invention provides an electrical steel plate and a preparation method thereof. The electrical steel plate comprises a plate-shaped electrical steel substrate, etching grooves on the surface of the substrate and CaSiO3 phases distributed on the surface of the etching grooves, wherein the thickness of the substrate is 0.1 to 2 millimeters, and the diameter of the CaSiO3 phases is 1 to 100 nanometers. The preparation method comprises the following steps of: 1) carrying out laser etching treatment; 2) processing the etching grooves with CaO powder, wherein CaO and SiO2 on the surfaces of the etching grooves react to generate the CaSiO3 phases on the surfaces of the etching grooves; and 3) washing and drying the electrical steel plate. The CaSiO3 phases have strong pinning effects relative to tensile stress or dislocation of regions around the grooves, a processed laser etching product has excellent thermal resistance, the iron loss reduction effect generated by laser etching cannot be disappeared after the product is subjected to thermal insulation and annealing treatment at 800 DEG C for 2 hours, and the original magnetic performance is basically maintained. The method is simple in operation, and production and application at a large scale are promoted.