Objective The performance of a cladding layer is significantly influenced by its microstructure. This study investigates the microstructure of a hollow ring laser cladding layer by examining the dendrite growth of IN718 alloy through macro-microscopic modeling and simulation, providing insights into the microstructural distribution of laser internal powder cladding layers. Methods Ansys software was used to calculate the temperature field results of the molten pool in the process of hollow ring laser cladding. The temperature field results were transformed by using the dynamic growth condition model of micro-structure, and the transformation results were put into the phase field model of micro-structure evolution modeled by MATLAB. The simulation results of micro-structure evolution in the process of hollow ring laser cladding are obtained and verified by experiments. Results In the process of hollow ring laser cladding IN718 alloy, the solidification process of molten pool is columnar crystal growth. The growth stages are linear growth, interface instability, competitive growth and stable growth. Conclusion With the solidification process, the concentration of the first solidified solid phase region is at the lowest, and the concentration of the later formed solid phase is increasing. When the dendrite growth enters the phase of interfacial instability, a large number of crystal nuclei will be generated at the diffusion interface. At this time, the initial columnar grains spacing is 1.202 μm, The columnar spacing reaches the maximum at the end of solidification is 8.307 μm.