The order-disorder transition at antiphase domain boundary (APDB) between DO22 (Ni3V) phases is investigated using the microscopic phase-field model. After the formation of ordered APDB, the order-disorder transition at APDB is happened, and the ordered APDB transforms into a thin disordered phase layer. Accompanied with the enrichment of Ni and Al at the disordered APDB, the second phase L12 nucleates at the order-disorder interface between DO22 phases and grows along the disordered phase layer. The order-disorder transition at the ordered APDB makes the nucleation and growth of the second phase L12 much easier and faster. The disordered phase caused by the order-disorder transition at the APDB can be considered as the transient phase during the precipitation process of L12 phase.