The solidification microstructures and their nucleation models are discussed,and the effect of the shape effect of moving melton pool on the solidification features is anslyzed on the basis of experiments. The experimental results show that its solidification behavior is complex,because the continuous laser alloying is a dynamical process. The reason for this complexity is that the dynamical solidification characteristic is significantly controlled by the laser alloying parameters and the molten pool shape. On the other hand,the solidification structures of laser alloying have a series of specialities,and their nucleation mechanisms are mainly heteroepitaxial growth and heterogeneous nucleation growth.