Abstract: A novel optical sensor for simultaneous measurement of voltage and current is proposed and demonstrated in experiment. The optical sensing unit is only composed of single bismuth silicate (Bi12SiO20, BSO) crystal and two prism polarizers. The BSO crystal exhibits both Pockels electrooptic effect and Faraday magnetooptic effect, thus voltage and current to be measured can simultaneously modulate the probing light wave when transparent axes of the two polarizers are parallel or perpendicular with each other. The frequency of current sensing signal is the same as that of the original current to be measured, meanwhile, that of voltage sensing signal is doubled. Thus current and voltage sensing signals can be simultaneously separated and measured by using two band pass filters. AC current and voltage with industrial frequency in the ranges of 6 A and 200 V were simultaneously measured in experiment by use of single BSO crystal with a size of 6.04.02.9 mm3.