The invention discloses an anti-dismantle tee operated without switching off an air source. The anti-dismantle tee comprises a first channel (1), a second channel and a third channel which are communicated with one another. A plug (2) is arranged in the first channel (1). A sealing piece (3) is arranged at an inner opening of the first channel (1). The anti-dismantle tee is characterized in that the sealing piece (3) comprises a sealing ring (3.1) made of elastic materials and a connecting piece (3.2) used for being connected with an opener; the sealing ring (3.1) is installed in the inner opening of the first channel (1) in an axially-limited mode, and at least one radial annular groove (3.1.1) is formed in the outer side wall of the sealing ring (3.1); the connecting piece (3.2) is connected with the middle of the sealing ring (3.1). According to the anti-dismantle tee, the aperture of the first channel with the sealing piece is increased to be greater than that of a ball valve element channel connected with the first channel, so that flow of the first channel is increased.