Metal films with a thickness as low as atomic layer have superior light absorption capabilities and conductive properties, especially the surface plasmons excited at the interface between metal film and dielectric can well capture photons and generate hot carriers, making them more efficient in improving the photoelectric conversion efficiency of solar cells, designing photodetectors in the near-infrared band, and sensors based on surface plasmon. However, there is still a lack of systematic theoretical studies on the surface plasmon and hot carrier properties of metal thin films. Based on the many-body first-principles calculation method, in this paper studied systematically are the surface plasmon properties of Au(111) films with thickness in a range from monolayer to 5 monolayers, and the energy distribution and transport properties of hot carriers generated by surface plasmons. The study results show that Au(111) films have low-loss surface plasmon properties. Meanwhile, the surface plasmons excited at the interface between the Au(111) film and the dielectric are strongly confined, which can enhance the local electric field, thus being crucial in nanophotonics applications. In addition, Au(111) film has a high efficiency generating hot carriers , and the generated hot electrons and hot holes are high in energy, and excellent in mean free path and mean free time. Unexpectedly, the direct current conductivity of Au(111) film is significantly better than that of bulk Au. These results provide new ideas and theoretical basis for the design and fabrication of Au(111) films in optoelectronic devices and energy conversion devices.