A　feedback　signal　of　the　rotor　radial　displacement　is　essential　for　realizing　the　stable　suspension　for　bearingless　flux-switching　permanent　magnet　machines　(BFSPMMs).　Although　the　recent　smart　sensors　technology　is　developing　rapidly,　the　mechanical　sensors　will　increase　the　complexity　of　the　system　while　reduce　its　reliability.　Thus,　an　alternative　is　urgently　needed　to　achieve　the　compact　and　practical　motor　structure.　Herein,　a　novel　rotor　radial　displacement　observer　is　presented,　and　a　radial　displacement　sensorless　control　system　based　on　the　observer　for　a　BFSPMM　is　built.　First,　the　mathematical　model　of　the　motor　concerning　rotor　eccentricity　is　established.　The　theoretical　expressions　of　flux　linkages　are　derived,　which　are　closely　related　to　the　eccentric　distance　and　angle.　Second,　the　rotor　displacement　signal　is　estimated　by　the　difference　of　the　symmetric-winding　flux　linkages.　And　a　closed-loop　compensation　method　is　designed　to　reduce　the　phase　lag　of　the　signal　in　the　observer　due　to　the　filter.　Besides,　the　convergence　regarding　the　proposed　observer　is　analyzed.　Ultimately,　the　observed　result　is　used　as　a　feedback　signal　to　control　the　suspension　force　of　the　system.　The　simulation　and　experimental　results　verified　the　validity　of　the　proposed　scheme.