Mechanical　systems　on　all　length　scales　may　be　subjected　to　nanoscale　thin　film　lubrication　(TFL).　Molecular　dynamics　(MD)　simulations　were　conducted　to　investigate　the　lubrication　mechanism　and　boundary　slip　of　squalane　confined　in　nanogap　at　293　K　with　two　different　film　thicknesses　and　a　wide　range　of　pressures.　The　molecular　distribution,　density　and　velocity　profiles　of　squalane　were　analyzed.　The　results　show　that　the　lubricant　atoms　tend　to　form　layers　parallel　to　the　wall,　but　the　lubricant　molecules　orient　randomly　throughout　the　film　in　the　directions　both　parallel　and　perpendicular　to　the　wall.　Most　squalane　molecules　appear　twisted　and　folded,　and　extend　to　several　atomic　layers　so　that　there　are　no　slips　between　lubricant　layers.　The　distances　between　the　lubricant　layers　are　irregular　rather　than　broadening　far　away　from　the　walls.　The　boundary　slip　at　the　interface　of　bcc　Fe　(001)　and　squalane　only　occurs　at　high　pressure　because　of　the　strong　nonbond　interactions　between　lubricant　atoms　and　wall　atoms.　The　tendency　of　boundary　slip　is　more　obvious　for　films　with　thinner　film　thickness.　According　to　the　simulations,　the　relationship　between　the　slip　length　and　the　pressure　is　given.　©　2020,　Wuhan　University　of　Technology　and　Springer-Verlag　GmbH　Germany,　Part　of　Springer　Nature.