The invention relates to the technical field of foundation pit supporting, and discloses a large-area foundation pit supporting construction method.A reinforcing mesh is arranged on a slope on one side of a
drainage ditch on the ground, soil nails are arranged on the reinforcing mesh, the reinforcing mesh is fixed through the soil nails, a concrete layer is sprayed to form
shotcrete-anchor supporting, and a waterproof curtain is arranged on the surface of the lower end of the reinforcing mesh; row piles are arranged on the inner side of the waterproof curtain and adopt cast-in-situ bored piles as foundation pit
fender posts, a soil body below a foundation pit excavation face on the inner sides of the cast-in-situ bored piles is reinforced to achieve passive area soil body reinforcement, a top beam is arranged at the upper ends of the cast-in-situ bored piles, a reinforcing
pier is arranged on the inner side of the top beam, and a steel lattice inclined
pile is arranged on the side, away from the top beam, of the reinforcing
pier. According to the construction method of the large-area foundation pit support, after the steel lattice inclined piles are put down, the reinforcing
pier construction reinforcing bars and the steel lattice columns at the tops of the steel lattice inclined piles are firmly fixed, and the top beams and the reinforcing piers are poured, so that the top beams, the reinforcing piers and the steel lattice inclined piles form an integral structure.