The principle of the distributed fiber-optic Sagnac location sensor is introduced.The structures studied at home and abroad such as single-loop Sagnac
two-loop Sagnac
merged Sagnac-Michelso and Sagnac interferometere hybrid Mach-Zehnder are analyzed
as well as location signal demodulation algorithm.The merits and drawbacks which need to be improved of fiber-optic distributed Sagnac location sensor are discussed.