Hydraulic　hammers　are　used　widely　now　in　construction　fields　such　as　road,　civil　engineering,　port,　and　mines.　How　to　design　them　optimally,　and　how　to　control　their　working　and　improve　working　efficiency　are　interested　to　many　researchers　and　manufacturers.　The　dynamic　characteristics　of　them　will　affect　their　performance　and　working　efficiency.　To　investigate　these　problems　and　to　improve　efficiency　of　their　analysis,　the　study　is　done　based　on　the　software　ADAMS.　According　to　working　principle　of　a　hydraulic　hammer,　a　dynamic　model　of　hydraulic　system　coupling　with　mechanical　system　is　established　in　ADAMS/Hydraulics　here.　Some　important　and　interesting　phenomena,　and　especially　its　dynamic　characteristics　are　found　by　study　of　piston　motion,　oil　flow　and　accumulator　pressure　in　the　hydraulic　system,　and　some　important　working　parameters　affecting　the　normal　working　of　the　hydraulic　system　are　also　found,　which　can　be　used　to　guide　optimal　design　of　hydraulic　hammers.　©　2010　IEEE.