For the measurement of AC current,the paper presents a current transformer based on giant magnetostrictive material (G MM) and fiber Bragg grating (FBG),which is used as the sensor probe,the ferrite material is applied to build magnetic system,and the narrow line width laser is used to realize the demodulation of FBG by locking the operating point.The current transformer can measure the f requency current,which can obtain good linearity within 0.33-100A,with 0.33% full scale accuracy.In thi s paper,the amplitude-frequency characteristics of the current transformer are focused by theoretical analysi s and experiment.The resonance frequency of 46.5kHz for GMM is obtained through simulation.The experimental re sults show that the current transformer has a flat amplitude-frequency characteristics within 5.0kHz rang e,the maximum measurable frequency can reach 20.4kHz,the resonant frequency is 46.5kHz,and it is suita ble for measuring high-frequency current.