Magnetostrictive sensor indicates a kind of displacement detecting device developed based on ferromagnetic material magnetostrictive effect. It could be used for continuously, precisely and real-time detecting the displacement (position) and velocity of various moving parts under abominably industrial environment. As an important component to realize precise operation and control, it can substantially enhance the precision and efficiency of the whole system. It is applicable for detecting the stroke or position of mechanical device with rectilinear motion. Precision servo feedback control of hydraulic system is one of the most typical applications.