An fiber current sensor is constructed by placing the gain magnetostrictive material (GMM) on fiber Bragg grating (FBG) system in current-induced magnetic field.The permanent magnet material is added at the two ends of GMM- FBG to form a static working point in bias magnetic field for the system.Besides,the GMM- FBG and permanent magnetic material are sealed by epoxy resin in order to insulate from external environment.Fiber Michelson interferometer linear sideband is used to demodulate the alternating strain on FBG to realize alternating current signal detection.The experimental results show that the maximum detected current is 1700 A and the voltage/current sensitivity is 0.68 mV/A when the system is working in linear region.The proposed current sensing device with simple structure,small volume and low cost provides an alternative choice for future current detecting device in power system.