Abstract: Refractive index is an important parameter for optical glass and there are many methods to measure the refractive index of optical glass. In order to measure refractive index accurately and quickly, a new method is introduced to measure refractive index of optical glass based on photo-electric technology. Optical flat has the feature of deviating incident ray, we can get the function of the offset distance and the refractive index, and the displacement fluctuation of light spot image is converted to electric signal outputting by a position sensitive detector. We designed an optical system and a signal detecting and processing circuit, measured the refractive index of K9 glass, and compared the results with the data measured by the method of minimum angle of deviation. The result proves this method is feasible, the accuracy of refractive index reaches 10-4, and it can be used to measure the refractive index of glass with high accuracy demand.