Abstract: A new double Fabry-Perot interferometer system with optical fibre for measuring micro-displacement and experiment study about its sensitivity threshold has been introduced in this paper.This system has the characteristics of high accuracy,interference-free compensation due to parallel double-channel configuration.Meanwhile the system may be suitable for accurate measurement of micro-displacement,such as calibration of displacement sensors,location in geometrical metrology,and for measurement of topography of fine manufactured surfaces and other physical quantities which could be transferred into displacement or optical path difference.