The invention discloses a device for preventing leakage during wall drilling. The device comprises a first leakage-proof plate, a second leakage-proof plate, a water inlet pipe, a ring-shaped elastic expansion surface as well as a water outlet pipe, wherein a leakage-proof hole is formed in the middle of the first leakage-proof plate; one end surface of the first leakage-proof plate is designed as a pasting surface; the pasting surface is used for being pasted on a wall surface; the leakage-proof hole corresponds to a to-be-drilled position of the wall surface; a clamping hole is formed in the middle of the second leakage-proof plate; the second leakage-proof plate is positioned on one side of the first leakage-proof plate, and arranged with the first leakage-proof plate at a certain interval; the clamping hole corresponds to the leakage-proof hole; one end of the water inlet pipe penetrates through the second leakage-proof plate and extends to the drill bit of an impact drill; the other end of the water inlet pipe is connected with a water source; the two ends of the ring-shaped elastic expansion surface are connected to the gap between the first and second leakage-proof plates in a sealing manner; a water inlet hole is formed in the lower part of the ring-shaped elastic expansion surface; and one end of the water inlet pipe is communicated with the water inlet hole. By adoption of the device, the defect that slurry generated during drilling by the impact drill scatters in all directions of the wall, and then the wall becomes relatively dirty can be overcome.