The invention relates to a cast-in-place slab without the need for a formwork and a construction method thereof. The cast-in-place slab without the need for a formwork comprises trusses, bricks, concrete and first steel bars, wherein the multiple trusses are transversely arranged at intervals; the multiple bricks are clamped between the adjacent trusses; the bottom surfaces of the bricks are flush with the bottom surfaces of the trusses; the bottom ends of the bricks and the bottom ends of the trusses form a bottom plate; the concrete is poured on the bottom plate; and the first steel bars are arranged in the concrete and located above the trusses and the bricks. The cast-in-place slab without the need for a formwork and the construction method thereof have the beneficial effects that the structure is simple, operation is convenient, labor and material resources are saved, resources are saved, the environment is protected, the construction method is simple, the slab achieves sound insulation, and a house achieves heat insulation and heat preservation.