A new type of voltage sensor which uses the prism and symmetrical metal-cladding polymer waveguide configuration has been proposed. The structure consists of a coupling prism and 3-layer film that prepared on the bottom of prism in proper order. The 3-layer films are metal layer, poled polymer, bottom electrode. Owing to the electrooptical effect of the poled polymer, and the sensitive feature of its refractive index to the resonance obsorption peak of the guided mode, the voltage change can be determined through the measurement of the light intensity when applying voltage on the poled polymer. The measurement range of voltage is from -140 V to 140 V in the experiment. The linearity is 0.991. The resolution of voltage measurement is 0.1 V-1. The sensitivity coefficients is about 0.0011 V-1. The experimental results show the fine linearity and the high sensitivity of the proposed voltage sensor.