Building foundation pit three-dimensional supporting system and construction method thereof

The invention discloses a building foundation pit three-dimensional supporting system which is characterized in that girders are transversely and fixedly erected on supporting piles around a foundation pit, anchor rods are connected to the girders at intervals, the anchor rods stretch into a soil body in a cable-stayed mode, structural steel is arranged in blocking parts in a driving mode to form reinforcing parts, and metal connecting parts pre-embedded in the supporting piles are provided with threaded holes; the bolt is fixedly connected with the metal connecting piece in a threaded mode, concrete is poured in the metal U-shaped piece to form a concrete solidification body, and the anchor rod, the connecting piece and the metal U-shaped piece are fixed into a whole through the concrete solidification body. The invention further discloses a construction method of the supporting system. According to the supporting system and the construction method thereof, the three-in-one supporting system of the supportin