Free　cooling　technology　can　effectively　reduce　the　cooling　energy　consumption　of　data　centers,　but　its　energy　efficiency　is　greatly　affected　by　regional　and　meteorological　conditions.　This　study　investigates　the　liquid-pumpdriven　free　cooling/mechanical　refrigeration　hybrid　cooling　system　of　a　data　center　with　40　racks　through　a　demonstration　case　and　tests.　The　annual　hourly　energy　efficiency　in　20　subclimate　zones　and　37　typical　cities　in　China　of　the　hybrid　cooling　system　designed　with　5　and　10　degrees　C　temperature　differences　was　analyzed　with　different　meteorological　parameters.　The　annual　power　usage　effectiveness　(PUE)　values　corresponding　to　the　energy　efficiency　ratio　(EER)　in　different　regions　were　presented.　Results　showed　that　the　annual　average　EER　of　the　liquid-pump-driven　free　cooling　mode　was　7.07-14.18,　and　the　annual　average　EER　of　the　hybrid　system　was　4.22-14.10　when　the　temperature　difference　was　5　degrees　C.　The　annual　average　EER　range　and　the　design　temperature　difference　of　the　hybrid　system　for　different　climate　regions　were　recommended.　The　PUE　values　of　other　regions,　except　for　Guangzhou　and　Haikou,　were　lower　than　1.40.　The　results　provide　references　for　the　EER　and　PUE　of　the　hybrid　system　in　different　climate　regions.