The machine (4) having an improved drainage grid (1) for compacting humid waste (2) comprises at least an Archimedes screw (7) which rotates internally of a containing structure (11) in which a support structure (13) is afforded for the grid (1). The drainage grid (1) comprises a perforated structure (16) shaped and connected to the fixed structure (13) in such a way as to maintain the perforated structure (16) continuously in contact with the helix (10) of the Archimedes screw (7).