Taking　the　cylindrical　roller　bearings　as　the　research　object,　considering　the　periodic　variation　of　the　roller　positions　in　the　circumferential　direction　during　bearing　rotating,　the　classical　theory　of　the　load　distribution　for　the　cylindrical　roller　bearings　was　modified.　The　time-varying　characteristics　of　bearing　stiffness　as　well　as　the　nonlinear　variations　of　average　bearing　stiffness　and　average　contacted　roller　numbers　with　radial　forces　were　analyzed.　In　order　to　verify　the　accuracy　of　the　modified　theoretical　method,　a　finite　element/contact　mechanics　method　was　utilized　to　analyze　the　cylindrical　roller　bearing　stiffnesses　and　roller　contact　conditions.　The　results　show　that　both　of　the　modified　theoretical　method　and　the　finite　element/contact　mechanics　method　may　accurately　predict　the　time-varying　characteristics　of　the　instantaneous　bearing　stiffness　and　the　nonlinear　features　of　the　mean　bearing　stiffness.　The　results　also　verify　that　the　changes　of　average　contacted　roller　numbers　are　the　primary　factor　of　bearing　stiffness　variations.　Based　on　the　modified　theoretical　method,　the　influences　of　bearing　initial　radial　clearances,　radial　forces　and　the　number　of　designed　bearing　rollers　on　bearing　characteristics　are　further　conducted　quantificationally.　©　2020,　China　Mechanical　Engineering　Magazine　Office.　All　right　reserved.