The invention discloses a lightweight high-performance foam concrete, which is composed of the following components in parts by weight: 50 to 60 parts of cement, 20 to 35 parts of mineral slag, 15 to 20 parts of fly ash, 5 to 10 parts of gypsum, 60 to 80 parts of fine aggregate, 2.7 to 7.3 parts of additive, 0.1 to 0.2 part of fiber, 32 to 45 parts of water, and 5 to 25 parts of foam. The invention also discloses a preparation method of the foam concrete. The foam concrete has the advantages of small volume-weight, high strength, low water absorption, and small contraction rate, and has the waterproof and anti-cracking functions at the same time.