The　impermeability　of　recycled　fine　aggregate　concrete　(RFAC)　with　different　contents　of　recycled　fine　aggregate　(RFA)　was　tested　according　to　the　standard　test　method　of　ASTM　C1202.　The　moisture　states　of　RFA　were　controlled　at　air-dried　(AD),　oven-dried　(OD)　and　saturated　surface-dried　(SSD)　states.　Both　the　interfacial　structure　and　the　pore　structure　of　RFAC　were　analyzed.　Research　results　show　that,　for　the　same　total　water-cement　(TWC)　ratio　and　the　same　content　of　RFA,　the　interfacial　transition　region　of　RFAC　became　denser　by　increasing　the　moisture　amount　of　RFA　from　oven-dried,　air-dried　to　a　saturated　surface-dried　state;　meanwhile,　the　density　and　porosity　of　hardened　cement　paste　(HCP)　improved　as　well,　which　resulted　in　the　higher　impermeability　of　RFAC.　Whereas　by　contrast,　for　the　same　moisture　state　and　by　increasing　the　RFA　content,　both　the　interfacial　transition　region　and　the　property　of　the　interface　structure　of　RFAC　became　weaker.　Also,　the　decreasing　density　and　porosity　of　HCP　resulted　in　lower　impermeability　of　RFAC.