The invention discloses a device for detecting mould impermeability, belonging to the technical field of mould. The device comprises a tank body which is communicated with a water inlet pipe, an air inlet pipe and a water and air outlet pipe. The water inlet pipe is connected with a water source. The water and air outlet pipe is connected with the mould. The air inlet pipe is connected with an air source. The device drives water into the mould by compressed air, thereby overcoming the disadvantage that the drive pressure of a water pump is too high as well as the disadvantage of the low efficiency of manual pressurizing.