In this article, a magnetic-focusing optical fiber current sensor based on the step-type magnetostrictive composite material is proposed, which solves the distribution problem of the current-induced magnetic field high at both ends and low in the middle on the conventional magnetostrictive composite material. Firstly, the magnetic field distribution model of the sensor is formulated by using the Ampere loop law. The theoretical analysis shows that the central magnetic field of the material is inversely proportional to the thickness of the material l 1 , the height of the bridge deck l 2 and the length of the bridge deck h1 . Secondly, the finite element simulation analysis is implemented for the key parameters of the sensor. Simulation results show that the material thickness l 1 , the bridge deck height l 2 and the bridge deck length h1 are the main influencing factors of the magnetic field in the center of the material. The magnetic field decreases with the increasing of the material thickness l 1 , the bridge deck height l 2 and the bridge deck length h1 , which is consistent with the theoretical analysis. Finally, the material is prepared and the performance test is carried out. Results show that with the increasing of current, the strain at the middle and both ends of the material increases gradually. The linear working range of the sensor is 0~ 1 000 A, and the sensitivity is 0. 136 με / A.