In　this　paper,　a　novel　density　sensor　based　on　high-birefringence　fiber　loop　mirror　is　proposed　and　studied.　The　high-birefringence　fiber　is　pasted　to　a　ring　shaped　rubber　gasbag　and　placed　in　the　liquid.　Fasten　the　gasbag　to　the　bottom　of　the　container.　When　the　density　of　liquid　is　changed,　the　liquid　level　keeps　the　same.　The　change　of　the　pressure　outside　the　gasbag　leads　to　the　variation　of　the　volume　of　the　air　in　the　gasbag.　Eventually,　the　strain　of　high-birefringence　fiber　varies　with　the　variation　of　the　volume　of　the　air　and　the　transmittance　of　high-birefringence　fiber　loop　mirror　shifts　with　the　density　change.　The　experimental　result　indicates　that　the　shifts　of　wavelengths　are　in　good　linear　relationship　with　the　density　of　liquid.　The　experiment　shows　that　the　sensitivity　is　8.024nm/(kg/m(3)).　The　novel　density　sensor　has　the　advantages　such　as　high　sensitivity,　polarization　independent,　low　cost　and　good　repeatability.