In order to obtain the spectral reflectance of ultraviolet and vacuum ultraviolet optical components, a set of reflectance measurement system is constructed. The reflectivity measurement system is composed of SeyaNamioka ultraviolet and vacuum ultraviolet monochromator, a sample turntable as the main body of the optic and electronic system. First, the system principle of measurement is introduced, the elimination of the light source with the time drift is by double light path compensation method, to obtain the reflected light and incident light data by changing the system optical path of two measurements, and then obtain the spectral reflectance. Then carries on the description to the electronics hardware system, gives the hardware design and the composition of the driver control unit and the acquisition signal processing unit. Because ultraviolet and vacuum ultraviolet spectral signal is weak, lock in amplifier is applied in the electronics system to improve the measurement accuracy. The test results show that the reflectivity measurement system repeatability of wavelength is 0.05 nm, measurement repeatability is 1.8%. The system stability is good, can realize high precision measurement of optical elements.