Abstract: Refractive index is one of the basic parameters of optical material. A device for measuring the refractive index in the UV waveband was developed based on right angle illumination method, in which an electro-optical stabilized sight was adopted to detect the ultraviolet (UV) light, a high precision goniometer with gas bearing was adopted to measure the angle, a lock-in amplifier was used to amplify the weak UV voltage signal, customized software was used to analyze the angle value and the variation of light intensity, and computer automatic control was incorporated to realize measurement automation. Refractive indices of quartz glass in 250 nm~450 nm were measured and the measurement results were given.