A roof reinforcing and leakage preventing device comprises a plate type roof, smoke discharging pipes, a double-clip type flange and feed-through bolts, and is characterized in that after openings are formed in the plate type roof, the smoke discharging pipes penetrate through the openings, the double-clip type flange is mounted at the top and the bottom of the plate type roof, the feed-through bolts are used for fixing the double-clip type flange and the plate type roof, so as to form surface contact, and the plate type roof can be less susceptible to deformation and tearing, therefore, the roof reinforcing and leak preventing effects are achieved. According to the roof reinforcing and leakage preventing device, the roof leakage preventing technology is adopted and the double-clip type flange is fully used for reinforcing the roof, so that the cut edges at the openings are changed to be in surface contact from line contact, and the contact area is increased. Therefore, the plate type roof is pressure-resistant and leak-proof, equipment failure caused when rain water enters into a workshop and electric elements can be avoided, and the production is stabilized.