Foundation pit reverse construction method cast-in-place pile sounding pipe hoisting positioning construction structure

The invention relates to the technical field of foundation pit cast-in-place piles, and discloses a foundation pit reverse construction method cast-in-place pile sounding pipe hoisting positioning construction structure. The structure comprises a pile hole, a pile casing, a steel reinforcement cage lowering in the pile hole in a suspension manner and an extension steel bar, the extension steel bar is hoisted to the position above the pile hole through a crane, the steel reinforcement cage is provided with a main reinforcement, and a bottom sounding pipe is fixed to the inner side of the main reinforcement of the steel reinforcement cage. The top of the bottom sounding pipe is exposed on the ground; the extension steel bar is connected with an extension sounding pipe, the lower end of the extension steel bar is fixedly connected with the upper end of the main reinforcement, the lower end of the extension sounding pipe is fixedly connected and communicated with the upper end of the bottom sounding pipe, and the