Stray current affects the safe operation of subway equipment. The stray current leakage point can be located by measuring the current of subway running track. A magnetostrictive current sensor with high sensitivity and a large linear range is proposed to monitor track current. The design of the sensor is qualitatively guided by a set of finite element method (FEM) simulations to improve the sensitivity of the sensor. However, when the sensitivity of the sensor increases, the linear range decreases. To solve this problem, a novel current sensor, to the best of our knowledge, which is composed of magnetostrictive composites, steel bars, and adjustable coils, is presented. The linear range of the sensor is expanded by adjusting the different DC bias magnetic fields generated by the adjustable coils. The results show that when the measured current is 0-500 A and 500-1000 A, the Terfenol-D (TD) mass is only 0.14 g, and the sensitivity of the sensor is 0.391 µɛ/A and 0.418 µɛ/A, respectively. The current measurement with low cost, high sensitivity, and larger linear working range is realized, which is suitable for monitoring stray current leakage points.