Boundary　lubrication　models　with　four　kinds　of　roughness　walls　were　established　respectively.　The　molecule　dynamics　method　was　used　to　quantitatively　analyze　the　density　distribution　of　three　base　oils　of　octadecane　and　its　isomers,　friction　coefficient　of　lubrication　systems,　adsorption　energy,　adsorption　time　and　diffusion　coefficient　of　stearic　acid;　meanwhile,　an　investigation　was　performed　on　the　adsorption　process　and　tribological　properties　of　stearic　acid　friction　modifiers　in　octadecane　isomeric　base　oils　restricted　by　rough　wall　surfaces.　The　results　show　that　the　molecular　structure　of　the　base　oil　and　wall　roughness　have　significant　effects　on　dclamination,　adsorption　and　tribological　performance　of　the　lubricants.　The　delamination　of　w-octadccanc　in　the　oil　film　is　obvious,　and　the　density　peak　near　the　wall　surface　is　large.　The　larger　the　wall　roughness,　the　weaker　the　delamination.　When　the　root　mean　square　roughness　of　the　wall　surface　Rq　0.　20　nm,　the　adsorption　energy　of　the　three　lubricants　consisting　of　octadecane　and　its　isomers　after　addition　of　stearic　acid　can　reach　the　maximum　value　and　the　friction　coefficient　will　reach　the　minimum　value,　respectively.　The　high-density　adsorption　layer　formed　by　base　oil　near　the　wall　can　inhibit　the　adsorption　of　stearic　acid.　For　the　3,5-diethyltetradecane　base　oil　with　long　branched　chains,　the　friction　coefficient　of　the　lubrication　system　is　the　largest,　the　adsorption　energy　of　stearic　acid　molecules　is　the　smallest,　the　adsorption　time　is　the　longest,　and　the　diffusion　coefficient　is　the　smallest.　The　long　straight　chain　molecular　structure　of　w-octadecane　results　in　the　formation　of　dense　adsorption　layer,　thus　hindering　the　adsorption　of　stearic　acid.　Stearic　acid　diffuses　fastest　in　2,4-dimcthylhexadecane,　whose　diffusion　rate　is　accelerated　with　the　increase　of　wall　roughness.　©　2023　Science　Press.　All　rights　reserved.