In　this　paper,　a　fiber　Bragg　grating　(FBG)　demodulation　system　based　on　high-birefringence　fiber　loop　mirror　(Hi-Bi　FLM)　is　proposed　and　demonstrated.　The　approximate　linear　edge　of　the　transmittance　of　the　Hi-Bi　FLM,　which　is　a　sinusoidal　function　of　wavelength,　is　used　to　interrogate　the　sensing　FBGs.　The　relationship　between　the　wavelength　period　of　the　transmittance　of　the　Hi-Bi　FLM　and　the　length　of　Hi-Bi　fiber　is　studied　and　the　results　shows　that　the　linear　range　of　Hi-Bi　FLM　is　in　Inverse　proportion　to　the　length　of　the　Hi-Bi　fiber.　To　get　wider　linear　range,　the　length　of　the　Hi-Bi　fiber　must　be　shorter　and　it　is　limited　by　the　fiber　fusing　technic.　Two　sections　of　Hi-Bi　fiber　is　orthogonal　fused　and　its　effect　is　equal　to　one　segment　of　fiber　whose　length　is　equal　to　the　difference　of　that　of　the　two　section　of　fibers.　Using　this　method,　a　Hi-Bi　FLM　with　a　wide　linear　range　of　20nm　is　made　and　used　to　demodulate　FBG　sensing　signal.　The　demodulator　has　advantages　of　all-fiber　design,　low　price　and　high　speed.