Pointing out the shortages of the traditional bar thread displacement transducer, brings forward new thought of designing difference phase degree division displacement transducer, which transforms the problem of measuring displacement directly in angle into the problem of measuring the difference between the phases of two signals which have the same frequency and then gets the displacement in angle indirectly. The theories on designing the phase difference calculation displacement transducer and correlation displacement transducer is suggested. Because the difference phase degree division displacement transducer, supported by the computer technology and the signal processing technology, adapts to the development of instrument's fictionzing and intelligentizings, it is an advanced technology.