As　an　important　component　of　atmospheric　particulate　matter,　aerosols　have　an　important　impact　on　the　atmospheric　environment　and　human　health.　The　hygroscopicity　of　aerosols　has　been　widely　researched　as　an　important　factor　for　its　survival　time　and　physicochemical　properties　in　the　atmosphere.　At　present,　the　researches　on　the　hygroscopicity　of　aerosols　is　relatively　simple,　and　the　influence　of　the　microstructure　of　aerosols　on　the　hygroscopicity　is　less.　Based　on　Langmuir　adsorption　model　and　Fick＇s　diffusion　law,　a　single　particle　gas-particle　interaction　model　was　established.　The　uniform　distribution　structure　of　aerosol　particles　(H2O/C2H2O4)　and　the　non-uniform　distribution　structure　(H2O/C2H2O4/H2SO4)　were　analyzed.　The　results　show　that　the　non-uniform　distribution　structure　of　aerosols　affects　the　speed　of　the　water　uptake　process.　For　aerosol　molecules　composed　of　ideal　fluids,　there　is　no　intermolecular　interaction　between　molecules,　so　the　water-particle　exchange　between　gas　and　particles　is　faster,　and　the　concentration　of　the　outer　layers　firstly　increases,　and　then　the　inner　layers　gradually　diffuse　outward　until　equilibrium　is　reached　for　the　difference　of　layer　concentration.　Comparing　with　the　large　particles　in　the　same　volume　ratio　the　water　in　small　particles　is　more　difficult　to　run　off　because　of　the　larger　contact　angle　and　surface　tension.　In　addition,　the　surface　area　of　the　large　particles　is　small,　and　the　rate　of　water　loss　is　low.　It　needs　more　time　to　reach　the　balance.　©　2020,　Science　Press.　All　right　reserved.