Abstract: A 3D phase-field model was established by coupling the CALPHAD thermodynamic database to investigate the effects of Cr content on the precipitation kinetics and phase transformation mechanisms of the α’ phase in Fe-Cr alloys during aging. The precipitation mechanism of the α’ phase was analyzed in conjunction with the phase diagram and free energy curves of Fe-Cr alloys. The results show that, during the aging process, a higher Cr content leads to a shorter precipitation time for the α’ phase. With the increase of Cr content, the volume fraction and average particle radius of the α’phase increase, while the number density first increases and then rapidly decreases. In addition, the changes of Cr content can cause the precipitation mechanism of the α’ phase to shift from nucleation and growth to spinodal decomposition, thereby affecting the coarsening, morphology and Cr composition of the α’ phase.