The invention discloses an optical differential protection device which comprises an optical signal generating unit, a first coupler, a second coupler, a first integrated optical unit, a second integrated optical unit, a first sensing optical fiber, a second sensing optical fiber, a first single mode fiber, a first reflecting mirror, a third sensing optical fiber, a fourth sensing optical fiber, a second single mode fiber, a second reflecting mirror, a first photoelectric detector, a second photoelectric detector, a modulation-demodulation module and a protecting logical judgment module. According to the optical differential protection device provided by the invention, current in a current-carrying conductor is converted into phase difference information of two polarized lights, and due to the arrangement of the positions, the winding directions and the winding turns of the sensing optical fibers, action current and braking current measurement required by differential protection is directly achieved on an optical path layer. The sensing optical fibers are used for achieving optical operation to action current and braking current required by the formation of differential protection on the optical path layer, moreover, ratio restraint is achieved by selecting sensing optical fibers with different characteristics and arranging the winding turns of the sensing optical fibers, and simplification to criterions of differential protection actions is facilitated.