High　speed　turbo-expander　is　an　essential　refrigerating　component　in　cryogenic　systems.　In　addition　to　thermodynamic　performance,　its　stability　in　transient　high　speed　operation　is　also　of　great　concern　for　its　comprehensive　performance.　Oil　free　foil　bearing　has　a　great　application　potential　in　high　speed　turbomachinery　by　virtue　of　its　high　stability　with　no　extra　external　supplying　gas.　In　this　paper,　finite　element　model　of　a　150　Nm3/h　cryogenic　turbo-expander　using　foil　bearing　for　air　separation　is　configured　for　a　case　study.　Influence　of　bearing　structural　stiffness　and　damping　characteristics　on　the　rotor-foil　bearing　system　are　evaluated　for　stable　operation.　Static　structural　stiffness　and　damping　coefficients　of　the　protuberant　foil　journal　bearing　and　thrust　bearings　are　obtained　from　the　static　loading　and　deflection　tests.　With　the　tested　coefficients,　rotordynamic　performances　of　the　rotor-bearing　system　is　analyzed　numerically　and　compared　with　the　transient　experimental　results.　©　2018　Elsevier　Ltd