Molecular　dynamics　(MD)　simulation　is　adopt　to　investigate　the　boundary　lubrication　behaviors　of　cycloalkane　lubricants　on　nanoscale.　The　effects　of　lubricant　molecular　carbon　content　and　loads　on　boundary　lubrication　are　studied.　The　boundary　lubrication　model　with　single　asperity　for　friction　analysis　is　set　up.　The　distributions　of　density　are　illustrated　in　the　direction　of　the　film　thickness　when　the　pressure　changes　from　25　to　500　MPa.　The　converse　shear　velocity　is　enforced　on　each　wall.　The　friction,　the　normal　pressure　and　the　stress　of　the　system　are　calculated.　The　results　show　that　all　the　four　cycloalkane　lubricants　are　stratified.　With　the　increase　of　carbon　content　in　lubricant　molecule,　the　trough　value　in　the　middle　of　density　distribution　curve　get　higher,　the　number　of　the　atoms　between　layers　get　larger,　and　the　stratification　become　less　obvious.　The　bearing　capacity　of　the　lubricating　film　increases　with　the　carbon　content　of　the　lubricant　molecules.　The　cyclohexane　and　cyclododecane　lubricating　films　are　successively　broken　at　50　MPa,　the　cyclotetracosane　lubricating　film　is　broken　at　100　MPa,　while　the　bearing　capacity　of　the　cyclotetradecane　exceeds　500　MPa.　The　friction　coefficient　of　cyclohexane　oil　film　under　boundary　lubrication　is　simulated,　which　is　in　accordance　with　the　experimental　measurement.　©　2020　Journal　of　Mechanical　Engineering.