An　ultrahigh-frequency　(UHF)　radio　frequency　identification　(RFID)　tag　antenna　that　can　be　placed　on　a　metal　surface　with　stable　performances　is　proposed.　It　is　made　of　a　modified　dipole　with　two　cylindrical　metal　grounds　on　both　ends.　The　cylindrical　metal　grounds　not　only　enable　the　antenna　to　roll　freely　on　a　metal　surface　with　the　stable　reading　performance,　but　also　reduce　the　antenna's　length.　The　proposed　tag　antenna　maintains　a　small　size　with　the　diameter　of　10　mm　(0.031λ)　and　the　length　of　45　mm　(0.137λ).　With　an　effective　isotropic　radiated　power　(EIRP)　of　4　W,　experimental　results　demonstrate　that　the　proposed　tag　can　achieve　a　maximum　read　distance　ranging　from　9.1　to　11.7　m　when　the　tag　rolls　on　metal　surface.　The　tag　has　the　advantages　of　more　compact　size,　better　reading　range,　and　excellent　rolling　capability　on　a　metal　surface　in　comparisons　with　the　state-of-the-art.　These　features　fulfill　the　emerging　demands　in　the　industrial　internet　of　things　field.　IEEE