One-step　thermal　evaporation　route　was　developed　to　produce　large　quantities　of　ultrathin　magnesium　oxide　(MgO)　nanowires　on　a　steel　mesh　substrate.　The　synthesis　of　MgO　nanowires　was　carried　out　in　a　tube　furnace　under　air　pressure　using　initial　N2　gas　at　900　°C　and　subsequent　N2/O2　atmosphere　reaction.　Scanning　electron　microscopy　and　X-ray　diffraction　show　that　the　products　are　very　pure　of　crystalline　MgO　nanowires　with　diameter　from　10　to　50　nm　and　lengths　range　from　several　hundred　nm　to　more　than　10　μm.　High-resolution　transmission　electron　microscopy　and　its　corresponding　electron　pattern　reveal　that　these　MgO　nanowires　are　single　crystals　with　preferred　growth　direction　along　〈1　0　0.　Field　emission　(FE)　properties　on　MgO　nanowires　show　that　its　emission　currents　density　can　reach　2.1　mA/cm2　at　electric　field　of　6.46　V/μm　and　have　a　very　low　turn-on　field　emission　(1.3　V/μm).　These　results　suggest　that　ultrathin　MgO　nanowire　can　be　an　excellent　FE　material　candidate.　©　2009　Elsevier　B.V.　All　rights　reserved.