After　the　Fukushima　nuclear　accident　in　2011,　the　safety　of　the　spent　fuel　pool　(SFP)　which　lost　the　cooling　function　and　feed　water　suffered　an　unprecedenled　threat.　Many　countries　paid　attention　to　the　safety　of　the　SFP.　Researches　on　improving　the　safety　of　the　SFP　have　become　the　important　topic.　In　China　analyzing　and　improving　the　safety　of　the　SFP　forCPRIOOO　is　one　sub-topic　of　them.　This　paper　gives　a　design　of　passive　air　cooling　system　for　CPRI01XI　SFP.　which　can　control　the　water　temperature　of　the　SFP　under　80°C.　Then　the　transient　analysis　of　the　CPRIOOO　SFP　with　designed　passive　air　cooling　system　will　be　done　in　statio　n　black　out　(SB　O)　accident　by　the　best-estimate　thermal-hydraulic　system　code　RF.I.AP5.　The　design　calculation　results　show　that　to　maintain　the　temperature　of　CPRIOOO　SFP　under　H0°C.　the　tube　numbers　of　the　SF　P　and　air　heat　ex　changers　are　6627　and　19086　respectively.　The　height　difference　between　the　bottom　of　the　air　heat　ex　changer　and　the　top　of　the　SF　P　heat　exchanger　is　3.8m　The　SFP　heat　ex　changer＇s　tube　number　decreases　as　the　height　difference　increases,　while　the　air　h　cat　exchanger＇s　tube　number　increases.　The　transient　analysis　results　show　that　after　the　SBO　accident,　a　stable　air　cooling　natural　circulation　is　established　The　surface　temperature　of　CPRIOOO　SFP　increases　continually　until　80.5°C.　which　indicates　that　the　design　of　the　passive　air　cooling　system　for　CPRIOOO　SFP　is　capable　of　re　moving　the　decay　heat　to　maintain　the　temperature　of　the　SFP　around　80°C　after　losing　the　heat　sink.