The invention discloses a high-strength coal ash calcium sulphate whisker aerated concrete block and a machining method thereof. The high-strength coal ash calcium sulphate whisker aerated concrete block is prepared from, by weight, 30-40 parts of river mud, 20-30 parts of coal ash, 3-5 parts of calcium sulphate whisker, 4-6 parts of cement, 3-5 parts of quick lime, 0.02-0.04 part of triethanolamine, 20-25 parts of crop straw, 1-1.5 parts of water glass, 0.2-0.5 part of hydroxypropyl methyl cellulose, 1-2 parts of additive, 1-2 parts of aluminum powder, 0.2-0.4 part of dodecyl salicylic acid, 0.01-0.02 part of polyoxyethylene aliphatic alcohol ether, 0.2-0.3 part of triterpenoid saponin, 0.01-0.03 part of calcium stearate and 0.02-0.04 part of benzotriazole. The aerated concrete block is small in drying shrinkage value and high in cracking resistance and water resistance, and all properties meet the national standard. Compared with existing products, the aerated concrete block has obviously higher strength.