The mechanical properties of materials are related to the integrity of interfaces (phase and grain boundaries). For substitutional alloys, the Kirkendall voids tend to form more easily at the phase boundary or grain boundary when the atomic mobilities of different species are unequal, which will degrade the bounding quality of interfaces. So far, there have many experimental studies on the evolution of Kirkendall voids and the formation mechanism. However, allowing for the fast process of the Kirkendall voids from formation to evolution, it is hard to capture such process in real experimental conditionals. So the formation and evolution mechanism of the Kirkendall void need to be studied. A binary phase field crystal model was used to simulate the process of void formation and expansion at phase boundaries induced by the Kirkendall effect. Simulated results show that for the low misorientation phase boundary (PB), the void moves toward the side with large atomic mobility (a phase) and the void shape evolves from the initial parallelogram to hexagon. The atomic annihilation rate around a void is faster than that of growth rate, which results in void expansion. The PB migration, phase growth and shrinkage can also be observed in void expansion. For the large misorientation PB, voids can also expand along the PB direction, resulting in the connection of voids, therefore, the PB is separated and presents zigzag shape. In the interdiffusion system, the free energy decreases. The descending speed of the free energy is almost equal for the low misorientation PB while is increasing for the large misorientation PB when the atomic mobility difference becomes larger. The descending speed of the free energy is proportional to PB misorientations. The PB void predicted from our computer simulation is consistent with the experiment observation.