Abstract: The present invention provides the Fabry-Perot (F-P) sensor compromising housing, measuring probe, longitudinal sling block, and displacement converting device. The optic fiber passes through upside sealing ring and extends into upside through hole with the optic fiber end surface disposed at the bottom; the upside of longitudinal sliding block is disposed with reflecting surface, thus a Fabry-Perot cavity is formed between part of the fiber end surface at the bottom of the fiber and the reflecting surface on the upside of longitudinal sliding block. The displacement converting device will convert the lateral slides of the measuring probe into the slides of the longitudinal sliding block, which thus changes the distance from the reflecting surface to the fiber end surface and changes the Fabry-Perot cavity length. Further, the sliding distance of the measuring probe can be calculated after the variation of the Fabry-Perot cavity length measured in according with the Fabry-Perot principle.