The invention relates to high-strength lightweight aggregate concrete and a preparation method thereof, and belongs to the technical field of building material concrete. The lightweight aggregate concrete is prepared from the following raw materials in parts by weight: 105-118 parts of cement, 180-185 parts of light coarse aggregate, 120-125 parts of fine aggregate, 65-70 parts of mineral admixtures, 9-24 parts of modified polypropylene fiber, 3.4-3.8 parts of concrete admixtures and 65-70 parts of water. The preparation method comprises the following steps that the raw materials are weighed according to the formula ratio, the light coarse aggregate is added into water accounting for one half of the total water amount for pre-wetting for 45-60 minutes, then the fine aggregate is added, stirring is carried out for 1-2 minutes, the cement, the mineral admixtures and the modified polypropylene fiber are continuously added, uniform stirring is carried out, then the concrete admixtures andthe rest water are added, and uniform stirring is carried out so as to obtain the high-strength lightweight aggregate concrete. The high-strength lightweight aggregate concrete and the preparation method thereof have the advantages that the strength is high, and the quality is stable.