The invention provides a combination optical element and an optical fiber current sensing device including a combination optical device. The combination optical element includes an electro-optic phasemodulator and a polarization-maintaining fiber coupler, the electro-optic phase modulator and the polarization-maintaining fiber coupler do not need fiber fusion, the distance between the electro-optic phase modulator and the polarization-maintaining fiber coupler is greatly shortened, and no melting point protection is required between the electro-optic phase modulator and the polarization-maintaining fiber coupler, reliability of the combination optical device is greatly improved, and at the same time, the effect of vibration on the measuring accuracy of an optical fiber current mutual inductor can be reduced effectively. The optical fiber current sensing device includes the combination optical device, a laser, a polarization-maintaining circulator, a polarization-maintaining fiber delay ring, a 1/4 wave plate, a current sensing unit, and a photoelectric detector, the structure is simple, the volume of the optical fiber current sensing device is effectively decreased by using the integrated combination optical device, and the integration degree of the optical fiber current sensing device is increased.