An　adjustable　journal　bearing　is　proposed　to　eliminate　the　influence　of　external　operating　parameters　(such　as　speed)　by　actively　adjusting　the　radial　clearance.　The　paper　introduces　the　structural　design　of　the　radial　adjustable　bearing　and　realizes　the　adjustment　of　the　radial　clearance　through　the　mechanical　transmission　mechanism.　Then,　it　introduces　the　working　principle　of　adjusting　bearing　radial　clearance.　Finally,　a　method　of　adjusting　the　radial　clearance　is　developed　by　studying　the　influence　of　the　radial　clearance　on　the　vibration　characteristics　of　the　system.　The　bearing　radial　clearance　has　a　great　influence　on　the　dynamic　characteristics　of　the　system.　The　essence　of　adjusting　the　radial　clearance　is　to　change　the　stiffness　and　damping　coefficient　of　the　oil　film.　In　order　to　study　the　influence　of　radial　clearance　change　on　system　stability,　a　two-degree-of-freedom　adjustable　bearing　model　was　established.　When　the　bearing　system　is　running　at　low　speed,　properly　reducing　the　radial　clearance　can　improve　the　stability　of　the　system.　When　the　speed　increases　and　the　instability　occurs,　the　radial　clearance　can　be　increased　through　the　optimization　adjustment　method　to　restore　the　bearing　from　the　high-speed　instability　state　to　the　stable　state.　According　to　the　research　results,　the　optimal　adjustment　method　of　bearing　clearance　is　determined.　Finally,　a　test　bench　is　built　to　verify　that　adjusting　the　radial　clearance　of　the　bearing　can　restore　the　stability　of　the　system.