In order to make fiber current transformer to have the ability to measure the current quickly and accurately,we analyzed the polarization-modulated all-fiber current transformer based on Faraday electromagnetic induction effect.And a dual optical path detection method is introduced.Polarized light from the optical fiber is divided into two beams.One is perpendicular to the direction of vibration,the other is at a certain angle towards the spread direction of the wave.After converting optic signal into electric signal,the sine wave signal obtained via amplification and filtering process is noiseless.Combining with TMS320F28335 test platform two output signals are synchronously acquired and demodulated,then the Faraday rotation angle is determined by calculation.And the relationship between fitting Faraday rotary and the reference current value is obtained.Finally the measurement system can measure current value in the high-pressure environment quickly and accurately.It proves that the system is applicable to large current detection in the high-pressure environment.