Underground space drainage system

The utility model provides an underground space drainage system, which belongs to the technical field of underground space, and comprises at least two drainage subunits, a drainage main pipe and a plurality of connecting pipes, each drainage subunit comprises a water storage cylinder, a clamping piece, a drainage sub pipe and a filter, each water storage cylinder comprises a cylinder body with the top open and the two ends closed and a top cylinder part movably embedded in the top opening of the cylinder body, all the water storage cylinders are arranged in a concrete layer under a water accumulation area in the underground space, the clamping pieces are columnar, and the lower ends of the clamping pieces are connected with the top cylinder parts of the corresponding water storage cylinders; the interior of the drainage sub-pipe is communicated with the space in the water storage cylinder, and the filter is arranged at the upper end of the drainage sub-pipe; the water storage cylinder in each drainage subunit