The utility model discloses a gravity type thick liquid sand separation system belongs to the building field, and it includes: drilling bored concrete pile machine, sedimentation tank, mud circulatorypool, waste residue collecting pit and thick liquid sand separation ware, between drilling bored concrete pile machine and the sedimentation tank, all be connected through the mud leather hose between drilling bored concrete pile machine and the mud circulatory pool, be provided with mud inlet, slurry outlet and waste slag outlet on the thick liquid sand separation ware, between mud inlet and thesedimentation tank, between slurry outlet and the mud circulatory pool, be connected through the mud leather hose respectively between waste slag outlet and the waste residue collecting pit, be provided with the slush pump between sedimentation tank and the thick liquid sand separation ware. In this way, the utility model discloses can solving current sedimentation tank, to deposit the effect poor, problem that the mud utilization ratio is hanged down.