The　inflatable　cover　was　used　in　the　low-temperature　blackbody　radiation　source;　the　function　of　the　external　gas　separation　had　great　influences　on　blackbody　radiation　source　performances.　This　paper　presents　a　new　way　for　performing　numerical　simulation　for　the　three-dimensional　inner　flow　field　analysis　of　new　inflatable　cover　and　blackbody　radiation　source　cavity　by　using　the　FLUENT　software　of　CFD.　By　comparison,　the　simulation　results　and　the　acetone　tracer　particle　experiments　revealed　the　reason　of　the　outside　air　into　the　cavity　caused　frost　and　dew,　so　we　proposed　a　number　of　methods　to　reduce　air　convection　inside　and　outside　of　the　cavity　for　the　using　inflatable　cover,　and　it　gave　theoretical　basis　guidance　for　the　next　optimal　design　of　the　new　inflatable　cover.