The invention relates to a foam concrete block produced with waste ash and a manufacturing method thereof. The manufacturing method is characterized in that waste ash, waste polystyrene foam, portland cement, calcium oxide, calcium sulfate, bentonite, polycarboxylate superplasticizer, sodium carboxymethyl cellulose, sodium lauryl sulfate, aluminum sulfate, sodium chloride, borax and water are used as raw materials, the raw materials are uniformly mixed by a double-shaft mixer into mixture, foam is prepared through mixing the mixture with sodium dodecyl benzene sulfonate and polyacrylamide, a computer is used for fully automatic control, the mixture is fed by a spiral tube conveyor into a high-speed mixing and soaking slurry-producing mixer and is mixed well into paste type foam slurry, the slurry is poured into a die, shaped and then delivered into a curing room for curing, the cured product is fed into a stripping machine for stripping, stacking, packaging and storage on a yard are performed after stripping, and thus the foam concrete block product made of the waste ash is prepared. The product has the advantages and effects of light weight, heat preservation, thermal insulation, sound insulation, capabilities of being nailed, sawn and processed into different specifications, high strength, no pollution, low cost and good profits, and complies with national requirements for energy conservation, emission reduction, development of the low-carbon economy and environmental protection.