Hopkinson　pressure　bar　experiments　of　oxygen　free　copper　in　high　speed　machining　process　were　carried　out　with　temperature　ranging　from　20　℃　to　900　℃　and　strain　rate　ranging　from　1.0×103　to　1.5×104　s-1.　The　true　stress-true　strain　curves　obtained　from　experiments　showed　that　the　mechanical　property　of　oxygen　free　copper　showed　obvious　strain　rate　and　temperature　sensitivity.　The　flow　stress　increased　significantly　with　the　increase　of　strain　rate　and　decreased　with　the　increase　of　deformed　temperature.　The　empirical　Johnson-Cook　constitutive　model　had　a　large　error　in　describing　the　dynamic　mechanical　property.　Based　on　the　analysis　of　dynamic　mechanical　property,　a　modified　Johnson-Cook　constitutive　model　was　proposed.　It　can　predicte　experimental　results　well,　and　then　can　be　used　to　simulate　dynamic　mechanical　property　of　oxygen　free　copper　in　high　speed　machining　process.　©　2018,　Shanghai　Jiao　Tong　University　Press.　All　right　reserved.