Magnetostrictive displacement sensors are used in shield tunneling for reliable absolute position feedback in harsh underground conditions. A tunnel boring machine needs precise hydraulic cylinder stroke control to maintain alignment, steering, and face pressure. Traditional sensors can drift, wear, or fail under vibration, moisture, dust, and electromagnetic interference. Magnetostrictive sensors measure the interaction between a magnetic field and a waveguide. A position magnet moves along the sensor rod, and the torsion pulse is converted into an accurate distance value. This design offers high resolution, long ranges, and repeatability. In shield tunneling, sensors are installed in hydraulic cylinders or on thrust and articulation systems. They monitor cylinder extension, shield articulation, and cutterhead support movement in real time. Accurate data helps automatic steering correct deviation, reduce overcut, and protect tunnel lining. It also improves safety by preventing sudden cylinder movement or excessive pressure. The sealed, non-contact sensing element resists oil, water, shock, and temperature changes. They support analog, SSI, CANopen, and other outputs for PLC and SCADA integration. Choose the right stroke length, pressure rating, IP protection, and signal interface. Regular calibration and cable protection extend life. As shield tunneling moves toward automation, magnetostrictive displacement sensors provide a strong foundation for precision, uptime, and low maintenance.