To enhance the output voltage amplitude of the magnetostrictive displacement sensor, the torsional strain of the waveguide wire is studied. Based on the related theories of electromagnetics and theoretical mechanics, a mathematical model of the torsional strain of the waveguide wire and a three-dimensional finite element simulation model are formulated. The factors that affect the torsional strain of the waveguide wire are analyzed. The corresponding output voltage of the sensor is obtained by experiments. Results show that the output voltage of the sensor is consistent with the change trend of the maximum torsional strain of the waveguide wire. The output voltage of the sensor and the maximum value of the torsional strain of the waveguide wire increase with the increasing of permanent magnet magnetization, permanent magnet geometric parameters, and permanent magnet placement angle. As the distance between the permanent magnet and the waveguide wire increases, it shows a trend of first increasing and then decreasing. Finally, it is determined that the permanent magnet has a length of 15 mm, a width of 10 mm, and a height of 5 mm. The length direction is magnetized 1T and the magnetization direction is perpendicular to the waveguide wire. The distance between the permanent magnet and the waveguide wire is adjusted to 25. 5 mm. And the torsional strain of the waveguide wire reaches a maximum of 3. 84×10 -4 mm, and the output voltage of the sensor also reaches a maximum of 0. 109 V. Research results provide guidance for reasonable selection of magnetization direction, magnetization size, geometric parameters, placement manner and distance between permanent magnet and waveguide wire.