Molecular　dynamics　(MD)　simulations　using　the　polymer　consistent　force　field　(PCFF)　were　adopted　to　investigate　the　density,　molecular　and　velocity　distributions　of　lubricant　squalane　in　nanogap　at　293　K,　three　different　film　thicknesses　and　a　wide　range　of　shear　velocities.　The　lubrication　mechanism　and　boundary　slip　were　analyzed.　The　results　showed　that　the　lubricant　atoms　tended　to　form　layers　parallel　to　the　confining　wall.　The　distances　between　the　layers　of　lubricant　atoms　were　irregular　rather　than　broadening　far　away　from　the　walls　and　were　about　three　to　four　times　the　length　of　C　C　bond　in　the　squalane.　The　tendency　of　lubricant　atoms　to　form　layers　and　the　density　of　solid-like　layer　increased　with　decreasing　film　thickness.　It　was　clearly　to　find　the　boundary　slip　at　the　solid-liquid　interface　from　the　velocity　profile.　The　slip　lengths　increased　with　increasing　velocity　of　substrates　at　the　beginning,　and　then　decreased.　When　the　film　thickness　was　3.44　nm,　the　maximum　slip　length　was　4.35　nm　at　the　substrate　velocity　of　22.8　ms-1.　According　to　the　simulations,　the　relationship　between　the　slip　length　and　the　shear　velocity　was　given.　©　All　Right　Reserved.