The precipitation and growth of V-concentrating phase are implemented in the synthetic V-bearing steelmaking slag based on the composition of factory slag from the Masteel Co. X-ray diffraction (XRD) and scanning electron microscopy (SEM), with energy dispersive X-ray spectrometer (EDX) are used to investigate the slag after heat treatment and to determine the temperature at which crystallization of V-concentrating phase is initiated. It is demonstrated Whitlockite with a high content of V₂O₅ (called V-concentrating phase) nucleates homogeneously and hetergeneously at 1623-1598 K. When emplaced holding time at 1548 K, the crystals of V-concentrating phase grow with increasing of the holding time using crystal size distribution theory (CSD). Observation of the microstructures and crystallite-size data indicates that the precipitation of V-concentrating phase proceeds via three different mechanisms: nucleation, growth, and coalescence of grains of V-concentrating phase.