Deep foundation pit supporting pile

The utility model relates to a deep foundation pit supporting pile which comprises a mounting bottom plate, a first square cylinder is arranged in the middle of the upper surface of the mounting bottom plate, L-shaped mounting frames fixedly connected with the upper end of the mounting bottom plate are fixedly connected to the two sides of the first square cylinder, and a first square extension column is slidably connected into the first square cylinder; a threaded groove is formed in the first square extension column, the first square extension column is connected with the first square cylinder through a lifting mechanism, first square frames are arranged on the two sides of the first square cylinder, two extension mechanisms are arranged between the first square frames and the first square cylinder, and sliding rods are slidably connected into the two first square frames; connecting blocks are fixedly connected to the surfaces of the upper ends of the sliding rods, and telescopic cylinders with the output e