The present invention relates to the technical field of head-up display, and particularly relates to a head-up display system for an automobile. The head-up display system comprises a projection light source and laminated glass, and further comprises a transparent nanofilm; said film comprises at least two dielectric layers and at least one metallic layer; the projection light source is used for generating p-polarized light; the p-polarized light is incident on a surface of an internal glass panel distal to an intermediate film, said light having an angle of incidence of 42 to 72 degrees, such that the transparent nanofilm can reflect part of the incident p-polarized light. The present invention markedly improves display quality and is suitable for high-definition image display. The structure and processes of the invention is quite simple. Head-up display functionality of high quality can be achieved merely by installing a projection light source capable of generating p-polarized light on a vehicle having a front windshield provided with a transparent nanofilm; thus the cost involved is extremely low. By combining various transparent nanofilm structures, monochrome display, multi-color display, and even full-color display may be achieved.