The invention discloses a super-light foam cement concrete and a preparation method thereof. The super-light foam cement concrete comprises the following raw materials by weight parts: 9-36 parts of dead burnt magnesium oxides, 9-32 parts of dihydric phosphates, 0.5-7 parts of adjustable solidification agents, 6-25 parts of light burnt magnesium oxides, 0.5-7 parts of sulfur-containing components, 1-25 parts of industrial slag powder, 1-20 parts of kieselguhrs, 0.3-3.9 parts of waterproof agents, 0.2-1.7 parts of foam stabilizing agents, 1.0-8.9 parts of foaming agents and 25-90 parts of water. The preparation method of the high-performance super-light foam cement concrete comprises the following steps of: metering raw materials; preparing the slurry containing the foam stabilizing agents; uniformly mixing the foaming agents; pouring and standing by; foaming and expanding; coagulating and curing; and naturally maintaining. The super-light foam cement concrete has the advantages of light weight, high strength, heat preservation and insulation, stable volume, low production cost, energy-saving property, no environmental pollution, and the like. The super-light foam cement concrete is simple in production process and is especially suitable for the heat-insulating material of external building wall, roof and floor.