A dust-proof device for machine tool worktable comprises a worktable, a worktable base, a stainless steel dust cover, organ-type dust covers and L-shaped dust-proof plates. The worktable base is installed on a machine tool bridge. The upper portion of the worktable base is provided with a U-shaped through groove. Two ends of the stainless steel dust cover are sealed by the L-shaped dust-proof plates. The upper portion of each L-shaped dust-proof plate is fixed on the lower side of the stainless steel dust cover, and the lower portion of the L-shaped dust-proof plate is fixed on the machine tool bridge. Each organ-type dust cover is disposed under the stainless steel dust cover and has one end connected to the worktable base and the other end connected to the L-shaped dust-proof plate. The worktable covers the stainless steel dust cover and is connected to the worktable base by means of bolts.