To enhance the analysis of the relationship between thermal cycle and crystallization in laser welding of amorphous alloys, a transient thermal model was established using ANSYS software′s Workbench platform, and the temperature field change process of laser welding of Zr63.7Cu17.5Ni13.1Ti3.9Fe1.8 amorphous alloy was analyzed. The temperature field and the sizes of melting zone and heat affected zone in the weld zone were obtained by simulation. The thermal cycle curves of several characteristic points were obtained by adding temperature probes. The thermal analysis was carried out according to the thermal cycle curves and DSC curves. Through the test results and analysis, it is found that the simulation results are in good agreement with the experimental metallographic images of the corresponding region, and the cause of crystallization in the heat affected zone is explained through the thermal cycle curve. Therefore, the study shows that given optimized and reasonable boundary conditions, temperature field simulation can predict the morphology and crystallization region of Zr-based amorphous alloy during laser welding. This insight could prove valuable for optimizing the welding process and guiding subsequent laser welding of the Zr-based amorphous alloy.