The invention relates to the field of building construction, and in particular to an internal permeation-proof curtain wall system. The internal permeation-proof curtain wall system comprises a supporting assembly which is connected with a building and a curtain wall, wherein the curtain wall is arranged on the supporting assembly; a water collection box is arranged under the curtain wall; a notchis formed in the water collection box corresponding to the lower edge of the curtain wall; the side wall, which deviates from the building, of the curtain wall is an outer wall, and the side wall, which faces the building, of the curtain wall is an inner wall; the outer wall of the curtain wall is matched with the outer wall of the water collection box; the inner wall of the curtain wall is communicated with internal space of the water collection box; water draining holes are formed in a bottom plate of the water collection box. In the internal permeation-proof curtain wall system disclosed by the invention, through the arrangement of the water collection box, the water collection box is arranged at the lower edge of the curtain wall, and the outer wall of the curtain wall is matched withthe outer wall of the water collection box, so that rainwater can be prevented from permeating into a room; by adopting the way, the structure is simple, and compared with a way of adding a layer ofcoating material or coiled material for water prevention on a whole outer wall surface, the construction cost is also greatly reduced.