By means of numerical simulation and process test, the change of temperature field and the effect on solidification structure evolution of BiSn alloy in 3D printing process were studied. The results show that each element node experiences several times of thermal shock during the forming process, and the amplitude of the whole thermal cycle curve becomes smaller and smaller. The first activated cell node experienced longer thermal action time and more times of thermal cycle shock. Under the technological conditions of 0.2 mm diameter of sprinkler head, movement speed is 2 mm/s, forming spacing is 2 mm, lap rate is 50%, 165 ℃ heating temperature and 100 ℃ forming base plate temperature, 3D printed metal parts with 97.6% densification can be obtained. By scanning electron microscope observation of the microstructure of the section of the formed metal, it can be observed that the microstructure of the bottom layer, the center and the upper layer are obviously different, and the microstructure of the central area is equiaxed crystal structure, which is consistent with the results of numerical simulation.