In ultraviolet photoelectron yield spectroscopy testing, ultraviolet light is employed to excite photoelectrons from materials, and the resulting data is processed to obtain the corresponding spectra. This paper presents a vacuum ultraviolet light source designed for photoelectron spectroscopy testing. The light from a deuterium lamp is focused onto the entrance slit of a monochromator using a toroidal mirror. The polychromatic light from the deuterium lamp is then dispersed by a holographic concave grating. A collimating mirror, a beam splitter, and a focusing mirror are utilized to form a 2×4 mm light spot on the sample, covering a wavelength range of 115-400 nm. The entire light source is divided into two paths: the main optical path and the reference optical path. The main optical path directs light onto the sample for testing, while the reference optical path monitors the deuterium lamp's degradation. The instrument is equipped with a broadband band-pass filter and an electronic shutter to filter out second-order spectra in the 115 nm to 200 nm range and control the light transmission in the main optical path. The paper also analyzes the energy transmission efficiency of the entire vacuum ultraviolet light source system and examines the impact of slit field of view on light collection. Finally, the photoelectron yield spectrum obtained using this light source is presented.