Displacement measuring method

The invention provides a displacement measuring method. The displacement measuring method includes: providing a displacement measuring system, wherein the displacement measuring system comprises a laser and a data acquiring and processing unit, and laser light output by the laser is divided into an o-light component and an e-light component with phase difference; via the data acquiring and processing unit, converting a light intensity signal of o-light into a voltage signal Vo, converting a light intensity signal of e-light into a voltage signal Ve, seeking a sum of light intensity of the o-light and the e-light so as to obtain a total power tune curve Vt, wherein Vt=V0+Ve; and judging a direction: seeking difference Delta (Vt) of the signal Vt, and calculating I, wherein I=Delta (Vt) x (Vo-Ve), when the value of I is larger than 0, the direction of the displacement is judged to be the first direction, when the value of I is smaller than 0, the direction of the displacement is judged to be the second directio