The invention discloses a fly ash/bentonite ceramsite concrete hollow insulation block and a preparation method thereof. The block is prepared from the following raw materials by weight: 100 to 150 parts of ordinary Portland cement grade 42.5, 500 to 600 parts of stone chippings, 30 to 40 parts of fly ash, 10 to 15 parts of bentonite, 5 to 10 parts of paper pulp waste liquid, 2 to 4 parts of nanometer alumina, 3 to 6 parts of light calcium carbonate, 20 to 30 parts of soluble glass, 10 to 15 parts of straw powder, 4 to 6 parts of a foaming agent, 1 to 2 parts of foots, 2 to 3 parts of a glass fiber, 0.5 to 1.5 parts of a redispersible latex powder and 150 to 210 parts of water. The boron fly ash/bentonite ceramsite concrete hollow insulation block produced in the invention has the advantages of high strength, low density, good heat insulation performance, good impact resistance, small possibility of water absorption, fire resistance, flame retardation, good weatherability, environment-friendliness, energy conservation and the like and has great market space and development prospects in the application field of building energy conservation in China.