Microstructure is one of the vital factors that determine the mechanical properties of magnesium (Mg) alloys. However, traditional microstructure characterization methods hardly satisfy the needs of tracking the morphological evolution of Mg alloys. With the rapid development of computer simulation, using the phase-field method to simulate the evolution of microstructures in Mg alloys has become the new norm. This article provides a review of the applications of the phase-field method in Mg alloys. First, classic phase-field models and the derived multi-phase and polycrystalline phase-field models are reviewed, then a review of the twin and solid-state phase transition phase-field models was undertaken, and the research progress of phase-field simulation in the solidification, recrystallization, and solid-state phase transformation of Mg alloys, were gradually introduced. In addition, unresolved problems of phase-field simulation were summarized, and the possible direction of future studies on phase-field simulation in Mg alloys field were discussed.