A headlamp unit based on a PBS includes a lens and a beam splitter. Viewed from a reverse light path, parallel light is refracted twice by an incident surface and an emergent surface of the lens and then converged in at least two focuses through the beam splitter. Each focus corresponds to a light path system, and the light path systems may be turned on simultaneously or separately to obtain a corresponding headlamp light pattern. Through beam combination of the PBS, two optical systems may achieve different illumination light shapes through on-off combination of light sources, and the two optical systems do not interfere with each other. The PBS obtains at least two accurate focus positions for the focuses of the lens, and an ideal light pattern may be accurately obtained. An upper beam light pattern may partially cover a lower beam light pattern.