The　Aw-Rascle　(AR)　model　has　attracted　more　and　more　attention,　because　it　solves　the　problem　of　the　anisotropic　property　of　traffic　flow　which　is　proposed　by　Daganzo.　The　AR　model　possesses　an　increasing　function　of　the　density　which　be　called　as　the　pressure　function.　The　calibration　of　the　pressure　function　is　a　primary　work　in　the　research　of　the　model　application.　In　this　paper,　we　calibrate　the　pressure　function　of　the　AR　model　via　flow-density　diagram　data.　Our　approach　is　to　rewrite　the　Lighthill-　Whitham-Richards　(LWR)　model　to　the　form　of　velocity　evolution　equation　which　based　on　flow-density　diagram　and　then　contrast　with　the　velocity　term　of　AR　model.　Finally,　we　employ　the　PeMS　detector　data　as　flow-density　diagram　data　to　construct　the　pressure　function,　and　apply　the　NGSIM　trajectory　data　to　be　the　initial　and　time-dependent　boundary　data.　Via　these　two　data　sets,　we　predict　the　traffic　state　at　interior　space　in　the　near　future　using　the　calibrated　AR　model　and　classical　AR　model　respectively,　and　compare　the　predicted　data　with　real　traffic　data　to　verify　the　feasibility　and　accuracy　of　this　calibration.