Based on the microscopic phase-field model, the precipitation process of Ni75Al4.3V20.7 alloy at 1190K is simulated, and the kinetics of order-disorder transition at antiphase domain boundary (APDB) formed between DO22 (Ni3V) phases is investigated. After the ordered APDB formed by the impingement of growing DO22 (Ni3V) domains, the order-disorder transition at APDB is happened. Accompanied with the enrichment of Ni and Al at the APDB, the ordered APDB transforms into a thin disordered phase layer. The second phase L12 nucleates at the order-disorder interface between DO22 and disordered phases, and grows along the disorder phase layer quickly. The order-disorder transition at the ordered APDB accelerates the nucleation and growth of L12 phase at the APDB. The disordered phase caused by the order-disordered transition can be considered the transient phase during the precipitation process of L12 phase.