The invention discloses a deep-lying karst region water seal reinforced roadbed structure. The structure mainly comprises a roadbed (1), a cast-in-situ concrete slab (2), a bore hole (3), a slurry radiation area (4), a water flow (5), a pre-stress longitudinal beam (6), a cave (7), an independent base (8), a pre-stress crossbeam (9), a grouting pipe (12) and a slurry radiation hole (13). The water flow (5) and the cave (7) are isolated by the slurry radiation area (4) through a curtain grouting technology to prevent the growth of the cave; and the pre-stress longitudinal beam (6) and the pre-stress crossbeam (9) are used in the roadbed area above the cave (7) to support the pressure applied to the cast-in-situ concrete slab (2) by the roadbed (2), and the independent base (8) provides supporting force for the pre-stress beams. The structure can effectively processes large caves with the depths being greater than 10 m, effectively isolates the water flow, prevents the growth of the cave, has guaranteed stability, is simple to construct, is economic and reliable, and has wide application prospect.