Laser cladding is an emerging environment-friendly advanced manufacturing technology that effectively solves the defect repair and strengthening of the nodular iron castings, improving hardness and wear resistance, and prolonging service life. Due to the strong heterogeneity of nodular iron structure and chemical composition, complicated cladding process caused by the carbon diffusion of the graphite phase, and the limited selection of cladding powder. It is difficult to obtain the transient evolution law of multi-field coupling in the cladding process only by material science experiments. Therefore, in this paper, numerical modeling and experimental analysis are combined to study the transient evolution mechanism of IN625 laser cladding on QT600 nodular iron.