The invention discloses a self-locking flange for isolating a spherical pig. The self-locking flange for isolating the spherical pig comprises a flange sheet (1), wherein the middle part of the flange sheet (1) is provided with a through hole (7); the flange sheet (1) is provided with a radial lock pin hole (8); the inner end of the lock pin hole (8) is communicated with the through hole (7); a self-locking pin (6) which is positioned circumferentially and can slide axially is arranged in the lock pin hole (8); a spring (5) for driving the outer end of the self-locking pin (6) to extend into the through hole (7) is arranged in the flange sheet (1); and the outer end of the self-locking pin (6) is provided with an inclined surface (9). The self-locking flange has a function of only allowing the spherical pig to pass through positively, and the problem of difficultly isolating the spherical pig is solved successfully. All spherical pigs needed by pipe cleaning operation can be loaded into a pipe scraper at one time, so that intermittent spherical pig ejection is ensured, the problem of difficultly isolating the spherical pigs is solved, a spherical pig loading flow is simplified, and the operation safety is enhanced.