The　research　of　modeling　agents　is　a　basic　work　of　agent　system　and　multi-agent　system.　So　far,　a　large　amount　of　models　have　been　proposed,　such　as　the　models　based　on　the　mental　states　(BDI)　of　Agents,　the　models　based　on　the　function,　which　maps　environment　states　or　percepts　to　action,　and　the　models　based　on　the　game　theory.　However,　almost　all　of　the　methods　merely　model　agents　from　one　aspect.　Thus,　they　don＇t　meet　the　need　of　complex　social　actions　of　agents.　(i.e.　coordination,　cooperation,　negotiation,　etc.)　Therefore,　in　this　paper,　we　combine　the　external　environment　state　with　agents＇　mental　states　and　utility.　And　we　propose　an　agent　model,　in　which　not　only　the　history　of　environment　and　the　history　of　action　are　considered,　but　also　the　mental　states　and　decision　utility　of　agents　are　considered.　The　balance　between　rational　consequences　and　rational　decision　utility　of　agents　was　found　out.　We　improve　the　models　proposed　by　Russell,　Wooldridge,　Rao,　Xu　etc　to　make　the　model　of　agents　meet　the　need　of　agents＇　interaction　with　others　in　the　complex　social　environments.　©　2005　World　Scientific　Publishing　Co.　Pte.　Ltd.