Air tightness detection device

The utility model discloses an air tightness detection device, which is used for detecting the air tightness of a cylindrical battery, the cylindrical battery is provided with a shell, the shell is provided with a first through hole, the cylindrical battery comprises a water tank with water inside, a jig arranged in the water tank and an air pipe for conveying air into the jig, the jig is provided with a second through hole, the second through hole is communicated with the air pipe, and the first through hole is communicated with the air pipe. A cavity for containing a cylindrical battery is formed in the jig, a sealing piece capable of deforming when stressed abuts against the inner circumferential wall of the cavity, the sealing piece is connected to the shell in a sleeved mode so that the sealing piece can deform, a sealed space is formed among the cavity, the shell and the sealing piece through deformation of the sealing piece, and the sealed space is communicated with the first through hole and the secon