Abstract: The ultraviolet (UV) image intensifier is the core device of the UV detection system, which is a kind of electric vacuum imaging device, and can transform and enhance the weak UV images into the optical images that can be detected by eyes. The development and application of the UV image intensifier is an important orientation of the low-light-level night vision technology. The radiant sensitivity is a key parameter to evaluate the UV image intensifier, which directly determines the performance of the UV detection system. The measuring principle of the radiant sensitivity for UV image intensifier was introduced, and the measuring system was constructed by the UV radiation source, grating monochromator system, testing dark box, micro galvanometer, computer and measuring software. The radiant sensitivity of three UV image intensifier at wavelengths of 260 nm, 280 nm and 320 nm was measured, respectively, and the measurement uncertainty was analyzed. The spectral range of the radiant sensitivity measuring system is extended to 200 nm～400 nm by the establishment of the measuring system, which makes up for the deficiency of the existing system and has broad application prospects.