This paper aims at the problems of low response sensitivity and poor temperature compensation effect of fiber Bragg grating (FBG) current sensor based on giant magnetostrictive material (GMM) to propose and design a double-ring lever type GMM-FBG current sensor. First, the theoretical model of the sensor is constructed and the influence of the distance between two silicon-steel sheets on the two FBG strain differences is simulated using COMSOL software to obtain a reasonable magnetic-circuit spacing. Second, parameters are optimized for the FBG grid length. Finally, considering the magnetic-circuit spacing and the FBG grid length, the relationship between the difference of two FBG strain variables and the measured current is obtained via simulation. The results show that at 16 mm magnetic-circuit spacing and 20?70 ℃ ambient temperature, the temperature change trends on the two FBG are the same. When the FBG grid length is 10 mm, the input current is 0?100 A, and the sensitivity of the sensor is 45.4 pm/A. When the resolution of the FBG demodulator is 1.64 pm, the minimum measurable current is 0.036 A.