The invention provides a strength controllable coal ash-based polymer concrete. The polymer concrete comprises a mixed solid phase and a mixed liquid phase, wherein the weight ratio of the mixed solid phase and the mixed liquid phase is 11:1, the mixed solid phase comprises the following components in parts by weight: 45-55 parts of coarse aggregate gravel, 13-33 parts of fine aggregate natural sand, 19-27 parts of coal ash, 0-8 parts of silica fume, and 0.05-0.12 part of sodium tripolyphosphate, and the mixed liquid phase comprises the following components in parts by weight: 67-75 parts of liquid sodium silicate for industrial use, and 25-33 parts of 10-18mol/L of sodium hydroxide solution. A preparation method for the coal ash-based polymer concrete is simple, has no toxicity and no contamination, and has low cost, and the raw material spreads all over the world and is expected to be used in fields such as corrosion resistant concrete construction, utilization of industrial wastes, rapid patching materials, high-strength high performance materials and the like. Furthermore, according to the coal ash-based polymer concrete, large amount of industrial waste coal ash can be efficiently used, so that the coal ash-based polymer concrete has great significance to conservation of energy and resources and environment protection. The invention also provides the preparation method of the coal ash-based polymer concrete.