In order to study the influence of the thermal accumulation effect of the multi-pulse nanosecond laser on the cladding process of the boron(B) doped silicon(Si) nano-film, the single-temperature model and the three-dimensional finite element method were used to numerically analyze the distribution of temperature field during the interaction process between the laser and the Si film, then the law of temperature field change under multi-pulse coupling was obtained. Compared with a single pulse, the simulation results of the multi-pulse laser action shows that the peak temperature has increased 3.2%, the size of the molten pool has enlarged 18.75%, and the range of the heat-affected zone has also significantly increased; after the laser irradiation, the surface temperature of the cladding layer drops, while the substrate temperature will continue to rise. The multi-pulse heat accumulation effect provides favorable conditions for the B diffusion in the Si nano-film. Finally, through single-pulse and multi-pulse laser cladding experiments, the different conditions of the cladding layers were analyzed, and the general law of the B diffusion assisted by laser cladding was obtained. The technology of laser-assisted B doped Si nano-film will provide the foundation for the applications in semiconductor devices.