Gravitational lensing is an interesting phenomenon in astronomy and is most typically given rise to by galaxies. The majority of the matter in a galaxy is thought to be dark matter, and the galactic gravitational lensing effect is mainly caused by dark matter halos. In gravitational lensing-related demonstrations in physics education, the feet of goblets are usually employed to simulate gravitational lensing, an approach that can seem unrealistic. This paper describes how the galactic dark matter halo model can be used to calculate an equivalent lens shape, and a stereolithography (SLA) 3D printer can then be utilized to create a "galactic gravitational lens" to simulate the gravitational lensing effect produced by real galactic dark matter halos. This method not only helps students gain a preliminary knowledge of gravitational lensing, galaxies, dark matter, and other astronomical concepts, but also increases their understanding of the application of 3D printing technology in the fields of mathematics and physical visualization.