The invention belongs to the field of concrete, and particularly discloses C140 high-strength concrete and a preparation method thereof. The concrete is prepared from the following materials in partsby weight: 490-570 parts of cement, 45-65 parts of coal ash, 100-120 parts of mineral powder, 65-85 parts of desulphurization ash, 20-40 parts of silica fume, 750-950 parts of coarse aggregate, 400-600 parts of fine aggregate, 5.5-7.5 parts of a water reducer, 10-20 parts of a corrosion inhibitor, 60-100 parts of fibers and 145-160 parts of water. The invention provides the C140 high-strength concrete; the concrete has a good slump, good extended degree, good compressive strength, and excellent comprehensive performance, and meanwhile, the problems of resource shortage of traditional cement admixtures of the mineral powder, the coal ash, the silica fume and the like, and limited resourced approaches and a low utilization rate of the desulphurization ash are solved.