Based on Giant Magnetostritive Materials(GMMs), a novel GMM-FBG (Fiber Brager Grating) current sensor with automatic temperature compensation is proposed by combing a sensing fiber Bragg grating (S-FBG) and an auxiliary fiber Bragg grating (A-FBG). The sensor cascades the S-FBG and the A-FBG and pasts them crossly on the GMM bars, then puts them into a magnetic circuit consisted of the ferrites. The radial direction of S-FBG is controlled the same as the direction of magnetic field, and that of the A-FBG is opposite with the former. Finally, the center wavelength of S-FBG is placed in the side-band of A-FBG spectrum, and current measurement and temperature compensation are implemented by detecting the optical intensity variation of cascaded gratings. The experiments are performed by the A-FBG and S-FBG with the 3 dB band width of 0.23 nm and 0.08 nm. The experimental results show that when the ampere-turns-current varies from 1 A to 138.2 A, the sensor can realize the linear measurement, and the goodness of fit is 0.996 3, the sensing sensitivity in the linear range is 16.0 mV/A and the minimum effective ampere-turn is 1.0 A.