Free　cooling　as　a　promising　technology　for　energy　conservation　is　applied　widely　in　data　centers.　A　loop　cooling　unit　driven　by　a　miniature　rotary　booster　for　free　cooling　was　developed　for　a　small　data　center.　In　this　paper,　compared　with　air　conditioners　and　pump-driven　loop　heat　pipe　units,the　booster　driven　loop　cooling　unit　consumes　low　power　and　has　a　high　energy　efficiency　ratio　(EER).　An　improved　rotary　booster　with　a　small　pressure　ratio　was　adopted　in　the　rotary　booster　driven　loop　cooling　unit.　The　results　indicate　that　with　the　increase　of　indoor　and　outdoor　temperature　difference　(?T),　the　unit　cooling　capacity　and　EER　increased　first　and　then　declined.　When　?T　is　25?,　the　cooling　capacity　reaches　17.7　kW　and　the　EER　is　15.2.　With　the　increase　of　?T,　the　power　of　unit　presents　the　downward　trend　all　the　time,　when　?T　is　25?,　the　power　of　unit　reaches　1.16　kW.　The　thermal　performance　is　compared　with　the　pump-driven　loop　heat　pipe　unit.　When　?T　is　25?　and　10?,　the　EER　of　the　rotary　booster　driven　loop　cooling　unit　is　25.5%　and　104.7%　higher　than　that　of　the　pump-driven　loop　heat　pipe　unit,　respectively.　©　ACRA　2018　-　9th　Asian　Conference　on　Refrigeration　and　Air-Conditioning.　All　rights　reserved.