The invention brings forward a vertical modulation reciprocity type optical voltage sensor. The vertical modulation reciprocity type optical voltage sensor comprises a sensing unit and an optical path unit which are connected through a polarization maintaining fiber. The optical path unit comprises a light source, a circulator, a Y waveguide modulator and a polarized light beam splitter. The circulator is also connected with a digital signal processor through a photoelectric detector. The sensing unit comprises a 45-degree Faraday rotator, a metal electrode, an electric light crystal, a transparent conductive film and a reflective film. The sensor employs a vertical modulation structure, i.e., the optical direction of the electric light crystal is parallel to the power field direction of the sensing unit. Such a structure prevents influences caused to a phase difference by nature birefringence of the electric light crystal, is free from the influence of nonuniformity of an external power field and an interelectrode power field, and improves measuring accuracy; and in addition, the sensor realizes mode switching of two beams of crossline polarized light by use of the Faraday rotator, a reciprocity type reflective optical path is formed, and the anti-interference capability of the optical path is improved.