Absorption　air　conditioning　system　could　be　driven　by　low　grade　energy,　such　as　solar　energy　and　industrial　exhaust　heat,　for　the　purposes　of　energy　conservation　and　emission　reduction.　Its　development　is　limited　by　its　huge　volume　and　high　initial　investment.　The　nanofluids,　which　possess　the　superior　thermophysical　properties,　exhibit　a　great　potential　in　enhancing　heat　and　mass　transfer　performance.　In　this　paper,　nanofluids　of　H2O/LiBr　with　Fe3O4　nanoparticles　were　introduced　into　absorption　air　conditioning　system.　The　effects　of　some　parameters,　such　as　the　flow　rate　of　H2O/LiBr　nanofluids,　nanoparticle　size　and　mass　fraction,　on　the　falling　film　absorption　were　investigated.　The　H2O/LiBr　nanofluids　with　Fe3O4　nanoparticle　mass　fractions　of　0.01　wt%,　0.05　wt%　and　0.1　wt%,　and　nanoparticle　size　of　20　nm,　50　nm　and　100　nm　were　tested　by　experiment.　The　results　imply　that　the　water　vapour　absorption　rate　could　be　improved　by　adding　nanoparticles　to　H2O/LiBr　solution.　The　smaller　the　nanoparticle　size,　the　greater　enhancement　of　the　heat　and　mass　transfer　performance.　The　absorption　enhancement　ratio　increases　sharply　at　first　by　increasing　the　nanoparticle　mass　fraction　within　a　range　of　relatively　low　mass　fraction,　and　then　exhibits　a　slow　growing　even　reducing　trends　with　increasing　the　mass　fraction　further.　For　Fe3O4　nanoparticle　mass　fraction　of　0.05wt%　and　nanoparticle　size　of　20nm,　the　maximum　mass　transfer　enhancement　ratio　is　achieved　about　2.28　at　the　flow　rate　of　100　L.h(-1).